Firefox 7.01 is having the same problem on my computer, which is an AMD 7750 dual core running 64-bit Windows 7 sp1. I tried uninstalling (completely, using Revo Uninstaller) and reinstalling which did not help, so I uninstalled again and went back to FF 3.6.23 which works fine, but now that I've experienced 7.01, I hope they fix this problem soon, because I love the way they have compressed the selections that used to take up multiple menu bars and thereby created a noticeably larger screenspace between top & bottom bars, plus 7.01 is definitely faster than 3.6.23. OK, you're wondering how I know if it won't start? Strange detail here is that the installer gives you an option at the end to open Firefox and that works just fine; it's only after you close it and want to open it again that I ran into the dll problem above. I don't know why it's doing it, of course, but isn't messing with dll's so ancient like DOS for example that we shouldn't have to be worrying about it anymore? Kind of undermines all the hype about how everything is more user-friendly now.

You will need to Reinstall Firefox because your previous Installation did not end properly or it got Corrupted.

-> Uninstall Firefox from your computer - Uninstall your current Firefox

• DO NOT SELECT TO REMOVE USER DATA AND SETTINGS
• Restart your system

-> Download latest Firefox version from one of these links using some other Web Browser:

• http://www.mozilla.com/en-US/firefox/new/
• http://www.mozilla.com/en-US/firefox/central/
• http://www.mozilla.com/en-US/firefox/fx/
• http://www.mozilla.com/en-US/firefox/all.html

-> Installing Firefox

• http://kb.mozillazine.org/Installing_Firefox

Check and tell if its working.