Start Firefox in Diagnose Firefox issues using Troubleshoot Mode to check if one of your add-ons is causing your 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 and Troubleshoot issues with plugins like Flash or Java to fix common Firefox problems

If it does work in Safe-mode then disable all your 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")

Thanks. It was Blacksheep (A Firesheep detector) that was the culprit.

walt

In my case the problem add-on was McAffee Site Advisor 3.3 in MS Vista OS.

Yes. It was Mcafee Site Advisor 3.3 for me too. But, for the record, this was happening in earlier versions of Firefox also. But it was the recent update of Site Advisor that was preventing the Bookmark menu from opening. I disabled it and all is well.

Thank you for posting your info about this. SiteAdvisor 3.3 for me also. Running 64-bit Win 7 Pro and FF 3.6.13. Nice to be able to decide where to put my bookmarks again.