Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance).

• Do NOT click the Reset button on the Safe mode start window or otherwise make changes.

• https://support.mozilla.org/kb/Safe+Mode

Try to disable hardware acceleration in Firefox.

• Tools > Options > Advanced > General > Browsing: "Use hardware acceleration when available"
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

• https://hacks.mozilla.org/2010/09/hardware-acceleration/

Now I use FF23 and it hangs shortly after starting it - it freezes about 3 seconds after it opened, and freezes for about 5-6 seconds, then it comes back to life. I suppose it is a problem with the video driver, as FF has once changed my cursor to a hand-like one. I have disabled video acceleration but with no effect. I have made custom changes to my NVIDIA control panel graphics settings, and I suppose that is one of the problems. On my NVIDIA GPU EeePC there is no such problem.

Can you try windows safe mode?

• http://windows.microsoft.com/en-us/windows7/start-your-computer-in-safe-mode

I restarted Windows in safe mode but no result. I have found what is causing the freezing though, it was the Lastpass add-on which was attempting to connect to the lastpass website every time FF starts. Here is the solution of the problem: http://www.imagebam.com/image/3c18fc271388433

But then, when I was uploading the image FF froze again, this time FF causing the video driver to fail (I have to say, that I enabled hardware acceleration again, after fixing the lastpass freeze): http://www.imagebam.com/image/9e5f52271389190

I forgot to mention - I use NVIDIA GTX560Ti, Intel Core i5 2500K, 16GB RAM and OCZ Vertex4 SSD with Windows 8 Pro x64 with all the latest drivers and firmwares installed.