Hi smoc,

You should look at the article How to fix preferences that won't save. It sounds like Firefox is just having trouble writing to the pref.js file.

Hopefully this helps!

I have followed the instructions in the article including deleting the prefs.js file with absolutely no effect. I also find that a "Welcome to Firefox" page opens each time I open Firefox, followed by a pop-up Powerfox window. When I close this window a Fasterfox pop-up appears. This is more than a little annoying and is now making me think that I will have to stop using Firefox, which I have used with only minor problems for several years.

Create a new profile as a test to check if your current profile is causing the problems.

See "Basic Troubleshooting: Make a new profile":

• https://support.mozilla.org/kb/Basic+Troubleshooting#w_8-make-a-new-profile

There may be extensions and plugins installed by default in a new profile, so check that in "Tools > Add-ons > Extensions & Plugins" in case there are still problems.

If that new profile works then you can transfer some files from the old profile to that new profile, but be careful not to copy corrupted files.

See:

• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox

I looked at all of the above articles and decided that I had no wish to create a new profile. I simply removed the Seven 2.0.2 appearance add-on and the problem seems to have vanished. (Touch wood!)