Two suggestions:
1) Reinstall the prior version of FF and see if it still runs. This will identify whether you have a different problem which just showed up at the time of the upgrade.
2) This will probably be fixed—but in the meantime, you could try Chrome.
I had the SAME exact problem. I had to uninstall and then re-install FF and it worked fine. Make sure and back up your settings if you wanna keep ‘em.
But once I did that, it ran perfectly and is so much faster than the 6.0.
I also run XP Pro btw.
Try this: uninstall your current version of Mozilla through Control Panel; also get rid of any program files in your Windows explorer folder. Restart the computer.
Then, using IE explorer, download the latest & greatest version of Mozilla....also the latest version of Adobe flash.
Good luck...
I do not have an answer but since this is a computer thread, I have a question that is unrelated to your problem. Does any one know where the info is stored on my computer? Specifically User Name and passwords for sites like FR or my Email program.
That happens occasionally.
It may be that a portion of FF is already running, thus preventing a new window from opening.
Right-click on the START Tool Bar and select Task Manager.
In Task Manager, select the Process tab. Click on Image Name to alphabetize. So down the list to see if firefox.exe is listed. If so, select firefox.exe and then select End Process.
After a few moments, try to load Firefox.
If it still won’t load, you may need to uninstall and reinstall Firefox.

as you have three browsers all on the fritz, it’s probably a add-on that’s causing it.
Probably Adobe Flash player.
Try to download and install the latest version:
http://www.adobe.com/support/flashplayer/downloads.html
if that doesn’t work, try this:
TO backup your firefox settings, go download and use mozbackup, http://mozbackup.jasnapaka.com/download.php
IDK how to backup Safari.
then uninstall, then reinstall firefox. same for safari.
Does the Application Event Log show any clues?
How odd is that? Since the problem is not firefox-centric... since Safari and Chrome are also effected... I find it hard to believe it was the Firefox update that did you in... UNLESS that update was a subsystem, and *not* Firefox itself. I would look for subsystems that effect all three, and not IE. The likely culprit would be Adobe Flash, with Java being a close second.
Try uninstalling Flash, using their universal uninstaller. This will fully uninstall BOTH the ActiveX (IE), and standalone (everything else) versions of Flash completely. RESTART. When done, Check for JOY. IF JOY, then you will have to re-install Flash in both IE and in Firefox (which will install also for Safari and Chrome) to get right.
If no JOY, next go to Add&Remove Programs, and uninstall ALL versions of Sun Java... and while you are there, any toolbars, especially oddball ones... RESTART. Check for JOY. IF JOY, reinstall the newest Java. Check for JOY. IF JOY, AND IF YOU REALLY MUST, reinstall toolbars one at a time, checking for JOY each time. If any one tool bar causes grief, uninstall it and leave it gone.
Look at RealPlayer, and any other subsystem (MediaPlayer add-ons, etc)that might effect all non-IE browsers, using the same uninstall, look for Joy, reinstall method.
If none of the above, I would sincerely be looking for a virus problem, or adware... Normally I would have this step first, but most bugs will crap out IE before any of the Mozilla based stuff.