Do you have that problem when running in the Firefox SafeMode?
http://support.mozilla.com/en-US/kb/Safe+Mode
Don't select anything right now, just use "Continue in SafeMode."

When in Safe Mode...

* The status of plug-ins is not affected.
* Custom preferences are not affected.
* All extensions are disabled.
* The default theme is used, without a persona.
* userChrome.css and userContent.css are ignored.
* The default toolbar layout is used.
* The JIT Javascript compiler is disabled.
* Hardware acceleration is disabled.

If not, see this:
http://support.mozilla.com/en-US/kb/troubleshooting+extensions+and+theme...

Safe mode has the same problem....tried most of what i could find on the net, even went as far as resetting FF. Not sure what to do...Id like to continue using FF but (as crazy as it may sound) this is a problem that will cause me to uninstall and not use again. Getting to my teams is just too important!

Those rollover menus are created via JavaScript, so make sure that you aren't blocking JavaScript.

• http://kb.mozillazine.org/JavaScript
• https://support.mozilla.org/kb/JavaScript

Also check your security software (firewall, anti-virus) to make sure that it isn't blocking such files if it happens with a new profile as well.

Try to do a clean reinstall and delete the Firefox program folder before reinstalling a fresh copy of Firefox.

Download a fresh Firefox copy and save the file to the desktop.

• Firefox 18.0.x: http://www.mozilla.org/en-US/firefox/all.html

Uninstall your current Firefox version, if possible, to cleanup the Windows registry and settings in security software.

• Do NOT remove personal data when you uninstall your current Firefox version, because all profile folders will be removed and you will also lose your personal data like bookmarks and passwords from profiles of other Firefox versions.

Remove the Firefox program folder before installing that newly downloaded copy of the Firefox installer.

• It is important to delete the Firefox program folder to remove all the files and make sure that there are no problems with files that were leftover after uninstalling.
• http://kb.mozillazine.org/Uninstalling_Firefox

Your bookmarks and other profile data are stored in the Firefox Profile Folder and won't be affected by an uninstall and (re)install, but make sure that "remove personal data" is NOT selected when you uninstall Firefox.

• http://kb.mozillazine.org/Profile_folder_-_Firefox
• http://kb.mozillazine.org/Profile_backup

• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Clean_reinstall

having a similar issue after the latest update. java is enabled. no firewall. worked fine before the update. the reinstall didn't help. :(

found the problem I think. I run scriptblocker and a script had gone from allowed to banned. don't know how the update could have affected that, but whatever. good to go now. :)