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

• Don't make any changes on the Safe mode start window.
• https://support.mozilla.com/kb/Safe+Mode

In Firefox 4 and later Safe mode disables extensions and disables hardware acceleration.

• http://kb.mozillazine.org/Safe_mode

Try to disable hardware acceleration.

• Tools > Options > Advanced > General > Browsing: "Use hardware acceleration when available"

If disabling hardware acceleration works then check if there is an update available for your graphics display driver.

I had already tried your suggestions before I posted the question. Still have the same problem operating in safe mode & turning off hardware acceleration also doesn't solve the problem. Any other suggestions.

Do a clean (re)install and delete the Firefox program folder (C:\Program Files\Mozilla Firefox\).

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

• Firefox 8.0.x: http://www.mozilla.com/en-US/firefox/all.html

Uninstall your current Firefox version if possible.

• Do NOT remove personal data when you uninstall the current version or you lose your bookmarks and other data in the profile folder.

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.

Your bookmarks and other profile data are stored elsewhere in the Firefox Profile Folder and won't be affected by a reinstall, but make sure that you do not select to remove personal data if you uninstall Firefox.

If the problem persist then try a new profile as well

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

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

Hi I tried all the above including a a completely clean copy of firefox & a new profile but nothing worked. Could it be something to do with windows? I tried using Internet explorer and the drop downs are working in it. I don't understand what could be wrong as it was working fine first thing this morning. I recall that I left the machine running with firefox open and when I came back & logged in to my user account on windows 7, there was an error message of some kind but I can't recall what it said. If I can't fix it I'll have to switch browsers which I don't really want to do as I like firefox. I know I don't have any viruses as I have a high level of security and I've done a complete scan.

I just downloaded & installed Chrome & found that I have the same problem with it. the drop down menus won't work so I'm thinking it must be something to do with how windows is interfacing with the web browsers. But I have no clue as to how to fix it. I appreciate you trying to help me though.

I have firefox 10.2 but I suspect this could be a Windows 7 issue