Please ensure that there are no anti-virus/firewall programs that are preventing Firefox from starting.

Logs are clean and I've tried running it with AV disabled.

Looks like the problem may have been introduced in 24; I was upgrading from 22. 23 starts but is somewhat crippled.

Traced a session in procmon; nothing stands out to me except a (rejected) attempt to claim write access to registry key HKLM\System\CurrentControlSet\Services\WinSock2\Parameters.

I have the same problem. I am using Firefox 25 on Win7 with no AV (just reinstalled) and it seems to have something to do with Java SE7 U45. Have also tried to clear cache and to start in safe mode.

After a reboot of the pc I can start FF but then suddenly if I close it and start again I have the problem.

Have you tried your computer in safe mode?
If not, please do so.

I have done so now. But in safe mode there is no internetconnection.

This is normal.
Does Firefox open in safe mode?

After 4 tries of opening Firefox I get the option of either resetting Firefox or disabling add-on. If I choose disabling add-on Firefox starts but the funny thing is that the add-ons are not disabled. Java e.g. is running.

Programs such as Java or Adobe Flash Play are not add-ons and will not be turned off in safe mode. These are known as plugins.
If Firefox has started in safe mode, please use trial and error to figure out which add-on is causing the issue. This can be done by using the add-ons manager in Firefox.

I do think I have found the problem. Apparently it has nothing to do with either add-ons or plugins.

Under Settings - Advanced - Generel there is the setting "use hardwareacceleration if possible". If that is not turned on it seems that my problem disappears

rasanna is referring to this:

Try disabling graphics hardware acceleration. Since this feature was added to Firefox, it has gradually improved, but there still are a few glitches.

You might need to restart Firefox in order for this to take effect, so save all work first (e.g., mail you are composing, online documents you're editing, etc.).

Then perform these steps:

• Click the orange Firefox button at the top left, then select the "Options" button, or, if there is no Firefox button at the top, go to Tools > Options.
• In the Firefox options window click the Advanced tab, then select "General".
• In the settings list, you should find the Use hardware acceleration when available checkbox. Uncheck this checkbox.
• Now, restart Firefox and see if the problems persist.

Additionally, please check for updates for your graphics driver by following the steps mentioned in the following Knowledge base articles:

• Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems

• Upgrade your graphics drivers to use hardware acceleration and WebGL

Did this fix your problems? Please report back soon.

Hi ComputerWhiz,

As you can see from my latest post I have already done what you are proposing and apparently that solves my problem.

Thx/Rasanna