Jeltz91, we do not really have any reason to expect your problem has the same cause as the one discussed in this thread. By all means read information in this thread and try the advice offered, but to solve your own problem it's best to start your own thread, by asking your own question with /questions/new.

Almost two months into this thread, and today you mention this.
"I also noticed in the 'System Requirements' page, it states :- Recommended Hardware Pentium 4 or newer processor that supports SSE2 - I don't have SSE2. Is this a problem? It says that SSE2 is a recommendation, but is mentioned in the 'requirements' page. Is it a recommendation or a requirement? "

Please download and run CPU-Z, and let us know which processor you have and if it supports SSE2.
http://www.cpuid.com/

SSE2 was introduced in 2001, in some Pentium 4 processors.
If you don't have SSE2, your computer just doesn't support Firefox 4+ versions.

Which WinXP Service Pack do you have?
SP2 or SP3 is needed for Firefox 4+ versions.

Did you try disabling the jscompiler by changing the pref ? To be honest, I can't remember how I did this now, but it involved changing the 'about' settings. Is Firefox 21 actually crashing, are you getting at least empty crash reports, or is it possible it is merely hanging ? It never produces crash reports despite setting it to do so. All that happens is the PC completely hangs - No disk activity, keyboard and mouse inoperative. Hangs may be slightly different problem. As hangs occur after startup it may be of interest to watch Firfefox's memory usage. It never hangs on startup. It is always after several minutes, but always within around 30. I have never seen less than 300meg of free memory being reported with or without FF running.

Almost two months into this thread, and today you mention this.

Nobody has ever suggested that this could be a problem before. I just happened to notice it today.

CPUZ info :- Name AMD Athlon XP Codename Barton Specification AMD Athlon(tm) XP 2800+ Package Socket A (462) CPUID 6.A.0 Extended CPUID 7.A Core Speed 2133.7 MHz Multiplier x FSB 16.0 x 133.4 MHz Rated Bus speed 266.7 MHz Instructions sets MMX (+), 3DNow! (+), SSE

If you don't have SSE2, your computer just doesn't support Firefox 4+ versions.

It doesn't say that in the specs, it says that SSE2 is recommended

IMO, when it comes to computer hardware "recommended" is the minimum specification.

There is usually startup code that modifies the file to use specific processor optimized code like SSE2 or SSE3, so I assume that it would work with a CPU that doesn't support SSE2, but performance will be slower.

You could try to start Firefox in a CMD.exe (command prompt) window to see if there is an error message about this.

I did read in http://en.wikipedia.org/wiki/Sse2#Notable_IA-32_CPUs_not_supporting_SSE2

The following CPUs implemented IA-32 after SSE2 was developed, but did not implement SSE2: 
    AMD CPUs prior to Athlon 64, including all Socket A-based CPUs .... 

I have certainly in the past run Firefox >4 on Socket A based CPUs

Yes, the startup code should check which features a processor supports natively and install emulation code for processor features that aren't supported.
Emulating specific instructions via multiple machine code (assembly) instructions is of course always slower, but ensures that the program is working with older processors.
This is comparable with hardware acceleration: if you turn off hardware acceleration then Firefox emulates this in software, i.e. use the CPU instead of the GPU.

It is quite apparent now that FF development is completely out of control. No-one has been able to explain why FF versions above 3.6.28 works on my PC. I see that FF is now up to version 22! How can it have gone up 19 versions in one year?! I have now ditched FF completely and have been using Chrome for over a month now with absolutely no problems whatsoever.

Every six weeks a new Firefox version gets released, so that would be 52/6 is about 8 versions a year.
So 19 versions should be about 2 and a half years (Firefox 3.6.28 was released in March 2012).

Every six weeks a new Firefox version gets released, so that would be 52/6 is about 8 versions a year. - Why? A new version should only be released when either a major fault is fixed, or several minor ones. This proves my point that FF is out of control, or more correctly, its development.

So 19 versions should be about 2 and a half years (Firefox 3.6.28 was released in March 2012). Do FF developers get paid for how many versions they produce? Nineteen versions in 16 months is one every 3 1/2 weeks approx. That doesn't sound stable to me. But what do I know, I only spent around 20 years developing software.

Hi rnewfie, you wrote:

No-one has been able to explain why FF versions above 3.6.28 works on my PC.

You confirmed that it works in Firefox's Safe Mode, which disables certain features of the browser, but if i recall correctly, you did not find the particular feature that is causing the problem (that involves making numerous manual adjustments; something might have been missed).

Have you tried disabling Hardware Acceleration? (Turning off hardware acceleration)

As for versions, we release a new version of Firefox every 6 weeks to get new features, bug fixes and improvements into the hands of users faster than ever before. You can read all our reasons for this change at https://blog.lizardwrangler.com/2011/08/25/rapid-release-process/.

rnewfie, no it is six weeks and not three and half weeks. The 3.6.28 and other 3.6.* should not really be counted as the updates for Firefox 3.6 were mainly for security (and not features besides 3.6.4 with plugin container) and originally could have ended at 3.6.19 about in security update but became the reluctant older supported version for a while after Firefox 4.0 was released.

corrected name.

(note that the name starts with "r n" and not a "m": "rnewfie") (I always copy/paste user names just to be sure)

I was on my PlayBook before and the default browser kept on trying to out-correct it to say Newfield at time. I decided to turn off the "Automatically correct as I type" in keyboard section as it was getting to be more of a pain versus helping.

"It is quite apparent now that FF development is completely out of control. No-one has been able to explain why FF versions above 3.6.28 works on my PC."

I've reached this conclusion as well. I've been using mozilla since 1999, and never had problems till about this year or last year. Firefox is dead to me. I used to use firefox on almost everything, but about half of my pc's have issues like this. In some cases, the system stops responding with the video frozen, and in other cases the screen goes black and windows says that the video driver crashed and was able to restart. This is unacceptable software development practice. There is no reason whatsoever to be releasing major revisions once every 6 weeks. I'd be much happier if we were still on version 4, because it would mean features were not being rushed and the result that end users are faced with would not be terrible. It's obvious that there are some major issues in firefox's hardware abstraction. I have these issues on Debian, Windows, and Mac OS on varying platforms ranging from Core i7 to Pentium M (Both of which support SSE2 I assure you). I really have no desire to contribute to a project with a release cycle of 6 weeks just for the sake of competing with google chrome's version number. Rather, I prefer to keep it in my pants.

I'm going back to using lynx on a tty because Microsoft has a terrible browser, Mozilla has given up on producing a good browser, and Google Chrome is a rip of an open source project that a company that I dislike is taking credit for. Pretty much no other browsers, opera etc. have the support to properly browse. So long graphical internet, It's been nice knowing you but obviously nobody cares any more.

Hi runfrodorun, I wonder whether you would consider using Firefox with the Shockwave Flash plugin disabled? It wouldn't be a pure textual web browser, but it might well resolve many of the issues you've been fighting while still giving you much of the modern web (e.g., what you could see on an iOS device).

The original poster in this thread is able to run newer versions of Firefox in Firefox's Safe Mode (hardware acceleration disabled, JavaScript compiler disabled, extensions disabled), so at least in theory, these problems could be overcome. But I understand it is a PITA to tweak numerous options if you are burned out on troubleshooting.

Nope. I've had hardware accelleration disabled, Flash is against my religion so it's not even installed and I don't have any other extensions installed. If the JavaScript compiler doesn't work there's no point to using the browser in the first place... unless my lack of html5 knowledge is making my ignorance too obvious

Honestly, it's much easier for me to just give up. I rarely run the X server on my pc anyways so lynx isn't a big deal. My experience in the software industry is that when the software starts to not work properly, abandon it. I've almost never seen a project turn around once it started to go downhill, except for in very large very financially and work-hour powerhouse companies, i.e. Microsoft. Case and point Windows Vista -> Windows 7, even though their difference is negligible. Free projects it's almost without exception. I don't realistically see anybody on top of the firefox development team to rethink the development philosophy of the project now that it's come this far, and without a new philosophy none of these problems are going to be properly addressed. I really appreciate your suggestions; but even if there is a chance that it might work it's not worth it to me at this point. I'm not prepared to support projects that are no longer going the direction they've been going, even if I've been using this browser or variants of it for 14 years. I'm really more just disappointed that it had to end this way. I'll always support the mozilla mission just not firefox.