Same thing here with XP SP3. Firefox 3.6.6 is very slow to launch (nearly 2 seconds), and was much faster before the update. I use only one pluggin.

After Mozilla automatically updated to 3.6.6 pages that would have taken 10 seconds to load in the past now can take 5 minutes or more to load.

If they don't fix the problems soon I'm going to have to switch back to using IE.

I experienced the same issue on 64-bit Linux (Arch) with KDE 4.4.5, after upgrading from 3.6.4. Start up was very slow (I could watch individual parts of the application being drawn). After waiting for the program to load, I tried changing the proxy configuration setting from "system proxy settings" to "no proxy", as another user suggested. The slowness instantly stopped (with no need to restart Firefox). Changing the proxy setting back to "system settings" and restarting Firefox again reproduced the slowness.

Didn't mozilla.org push a debug build by mistake?

Clean install solved the problem.

Please provide a fix or the means to remove 3.6.6 and reload an earlier trouble-free version

Since the "downgrade" to 3.6.6 all video is slow or unviewable and Firefox uses between 445mb to 610mb. That is up from 210mb to 260mb. I thought it was only Microsoft that screwed up updates! Very disappointing and I might have to change browsers as this is ridiculous. This computer has never had problems with speed but this has certainly changed that.

I'm using a plugin called Yslow. It gives you page size and load time for each web page. I really just wanted to see why Digg and TMZ were so slow.

When the page is loading in Firefox you can't scroll up and down. It's like the browser is locked up. TMZ was almost unusable today.

OK, I've moved back to 3.5.10 and operational problems I've been experiencing since the various "upgrades" (the recent severe slowness, particularly typing into text input boxes) as well as malfunctions in hotmail reply (missing original message) are out of my way.

I also noticed significantly reduced memory demand (right now, about 65M RAM vs. 120+ before I reverted to 3.5.10). This is important because my machine (win 2k sp4, 650 MHz, 512M RAM) is highly resource limited, and I'd suspect just shoveling all of the extra RAM around on behalf of firefox caused some of the overall bad experience.

Ever since 3.6.6 FireFox is SLOW!!! Very slow!!!

I had to do a Safe Mode Restore (Vista) after the last version because of a blue screen crash, and all this does not sound promising. Perhaps it is time for a Back To Basics Firefox.

Problem has occurred on both work and home PCs.

Fortunately, in both cases, I ran FEBE and OPIE extensions, so I was able to uninstall and reinstall Firefox entirely. That seems to have addressed the issue. I'm now running 3.5.10 Portable at home and 3.6.4 (normal) at work, both without problem.

From most accounts, the 3.6.4 to 3.6.6 upgrade was painless, but for a select few (us), something internally got buggered with the plugin container. Before regressing to a previous version, just starting Firefox up to a blank screen was taking 1400MB of memory. That's one and a half gigabytes of RAM, with no content. I'm now running 3.6.4 with four tabs, one of which is GMail, and it's using 200MB. I consider 200MB to be a pig too, but it's one seventh the consumption of 3.6.6, and unlike 3.6.6, it's actually serving up web pages.

Too many browser crashes/freezes, horribly slow : reverted to 3.6.2.

Can anyone recommend a video/audio recorder that would be compatible with Firefox, now that I lost my trusty Ask & Record Toolbar thanks to the automatic update of Firefox 3.6.6?

Even if I were to install an older version of Firefox I still would not be able to reinstall the Ask & Record Toolbar since it has been replaced by Freecorder, which I have heard doesn't even work.

What really pisses me off,is that I can't record off you tube or any sites off New York magazine.

It's a mess !!!!!

Same issue, windows XP 64, since 3.6.6 it just keeps freezing/hanging for 10-20 seconds all the time. It's not even usable.

Ok, just noticed in the troubleshooting section about addons causing problems. Disabled a bunch of them and now firefox is flying again. Suggest everyone try disabling all addons, then re-enabling one by one til the slowdown reoccurs.

Well, my question is when (If ever) Mozilla will give updates that don't kill addons???

Never experienced this much CPU usage with Firefox, even with just Google.com open in 1 tab. It's going nuts haha. (been a user since 1.0)