Please uninstall Firefox. Then Delete the Mozilla Firefox Folders in C:\Program Files and C:\Program Files(x86) Then restart system. DO MAC EQUIVALENT Note: your Firefox Profile is saved. But you should make a back up before you do :

• https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles
• https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer

Reinstall with Current Release Firefox 57.0.4 with a Full Version Installer

• https://www.mozilla.org/firefox/all/

Please let us know if this solved your issue or if need further assistance.

Thank you I tried that already, and it didnt' solve the problem. I have the same problem I home using Mavericks...

Did you delete the folders and did you use the full version installer as that is what makes it work.............

sorry for the late answer, I was away from my desk. I did as you said and deleted all the files and it solved the problem. Thanks!

Hello, OK so when I do the full reinstall (then I have to recover the bookmarks, certificates and passwords...), I works for a while, and then the drop down menus are incomplete again. I did a full (2nd time) reinstall a week ago, and the problem has come back... I am running Firefox Quantum 58.0.2, on a Mac with High Sierra. I don't have this problem at home where I didn't upgrade to high Sierra... don't know if that's related.

I am thinking using Chrome as default browser, but I'd rather stick to FF if you can help...

Thanks!!