Are you sure this happens in Firefox 3.5 but not 3.6?

It sounds like https://bugzilla.mozilla.org/show_bug.cgi?id=529655 which is not specific to 3.6.x.

In any case if it only happens with one add-on Options button, it is a problem with that add-on. You should contact the add-on author. Either their add-on has a bug (bad optionsURL in install.rdf), or they are missing a file (chrome.manifest).

This is happening for me with all add-ons, but only since my June 24th update to Firefox 3.6.4 . When I opened Firefox after the update, all traces of my add ons were gone (Zotero, StumbleUpon, ForecastFox, Delicious Bookmarks), despite it saying that they were installed in the add-ons window. Neither uninstalling and reinstalling individual add-ons, nor all of Firefox, nor uninstalling Firefox and re-installing Firefox 3.5 worked to fix the problem, and when I enter the add-ons window and click options on any of the add-ons, that window freezes, and despite the main Firefox window still being functional, Firefox must be restarted to unfreeze the add-ons window. I'm mostly concerned that all evidence of my add-ons has disappeared.

That but described part of my problem, but it didn't seem to get the whole show, nor provide a solution.

Any thoughts?

• • UPDATE**

How could this answer possibly solve the problem? I just restated the question! If I did provide the answer, help me help myself please!

I am having the same problem under 3.6.11. I have checked ALL of my add-ons and they HAVE chrome.manifest files. This bug may resemble the one in 529655, but it is not a duplicate because it is not functioning the same way. It may be failing in the same way because it is not finding the chrome.manifest files, not because they don't exist.

Also, my extensions do not appear to be functioning, whether I can access the options button or not. I have been using Greasemonkey for a long time, and it has worked perfectly. When I updated to 3.6.11, I noticed that the icon was no longer present, and this option-button bug surfaced for ALL add-ons. Also, my Delicious.com addon ceased to function at the same time, and could not be reactivated.

I suspect this may have something to do with the functionality recently installed to prevent "stealth" installs of add-ons. I would suggest looking in that area, where it might be overlapping the code that checks the location of the chrome.manifest file and the validity of the add-on at startup. The add-ons aren't starting at all, valid options cannot be accessed, and the problem started about the time the whole Microsoft stealth add-on issue (NO, I DON'T want to debate whether it was actually a "stealth" add-on or not, THANK YOU -- trolls kindly remain under your bridges!) came up.

Add-ons window freezes when I try to install zotero. It worked before the recent firefox update.