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

• Don't make any changes on the Safe mode start window.

See:

• Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems
• Troubleshoot issues with plugins like Flash or Java to fix common Firefox problems

If it does work in Safe-mode then disable all extensions and then try to find which is causing it by enabling one at a time until the problem reappears.

• Use "Disable all add-ons" on the Safe mode start window to disable all extensions.
• Close and restart Firefox after each change via "File > Exit" (Mac: "Firefox > Quit"; Linux: "File > Quit")

Hi cor-el, Thanks for the response. I started Firefox in Safe Mode and made sure I was using the Default theme (I don't have any other themes installed). Opening Tools -> Options made FF hang. Then I opened in Safe Mode & set all extensions to disable, reopened in regular mode, viewed Tools -> AddOns and verified all extensions and add ons are disabled. Tried opening Tools -> Options and FF hung. FF also hangs when I try to download a file. My problem seems to be similar to the following posts (which have no solution): https://support.mozilla.com/en-US/questions/714223?s=hanging+on+options&as=s https://support.mozilla.com/en-US/questions/687236?s=hanging+on+options&as=s

I can run version 3.5 ok but not version 3.6. Any thoughts?

Try to delete prefs.js and downloads.sqlite in the Firefox Profile Folder

If that doesn't help then create a new profile.
See Basic Troubleshooting: Make a new profile

Still no luck. Here's what I did: 1. Uninstalled Firefox 3.6.13 2. Deleted prefs.js and downloads.sqlite from profile folder 3. Rebooted computer 4. Turned off antivirus (Kaspersky IS 2010), re-installed FF 3.6.13 5. Same issue (hang on Options or Downloads) 6. Created new profile 7. Started FF w/ new profile 8. Same issue

Interesting to note - I was going to create the new profile in a different directory but as soon as I clicked the button to selected a different location the Profile Manager hung. I was briefly able to open Tools -> Options the first time but as soon as I clicked on the 'Applications' tab FF hung and continues to do so.

Try to delete mimeTypes.rdf as well.

Don't waist too much time in trying to repair that apparently broken profile, but try a new profile and then at least you know that the problem comes from your current profile or from elsewhere.

Do not create a new Profile in a different directory! If you don't create folder ahead of time for that new Profile, and you ever decide to delete that Profile, you could be deleting everything in that particular folder that isn't even related to Firefox.

That information is here -https://support.mozilla.com/en-US/kb/Managing%20profiles#w_creating-a-profile - in Firefox support.

3. ...
Note: If you choose a custom location for the profile, store it in a new or clean folder. When you choose to remove the profile, all contents stored in the same folder are removed.

Thanks for the note about profile locations.

I deleted mimeType.rdf in my existing profile, still have the same issue - can't view Tools -> Options for the Applications tab, or download a file. Same goes for a new profile - the same issues arise.

Firefox never does crash, I can leave it in this hung state for hours (I left it in a 'not responding' state last night and it was still hung this morning).

I was going to add a screen shot to this post but Firefox hung when I clicked on the 'Browse' button. Perhaps this is an issue when FF tries to interact with my directory structure? Does that get us any leads on what's wrong?

FYI, I currently have my antivirus disabled & not running in the task bar just in case that was interfering somehow.