Preferences not saved
This article deals with Firefox or Mozilla Suite not saving any changes made to options or preference settings after you restart the application. If you have problems changing only certain settings and your profile folder includes a user.js file, see Resetting preferences. If only Firefox toolbar customizations are not saved, see the article, Toolbar customizations reset on startup.
Read-only preference file
The inability to save preference changes can be caused by having the prefs.js or "prefs.js.moztmp" file in the profile folder set to read-only. You may receive an error similar to "Failed to save the preferences file. Any preference changes will be lost at the end of the session" [1]. You may also find multiple files named "prefs-n.js" (where n is a number) appearing in the profile folder.
Check the file properties of the prefs.js file and any "prefs.js.moztmp" file found and remove the "read-only" attributes to resolve the issue.
Note that other read-only files in the profile folder can cause similar problems, for example, a read-only cookies.txt or "cookies.txt.moztmp" file can cause loss of cookie data and creation of multiple cookies files and a read-only bookmarks.html or bookmarks.html.moztmp file can cause bookmarks not to be saved and creation of multiple bookmarks files.
Dell Network Assistant
Dell Network Assistant may also cause this problem. If you have this program, try uninstalling it.[2]
Related bugs
- Bug 157152 - read-only/hidden bookmarks.html (or bookmarks.html.moztmp) causes creation of bookmarks-{n+1}.html
- Bug 257288 - read-only profile files (cookies, bookmarks, etc) not respected, results in data loss
