See this article for some suggestions: Firefox says it's just updated every time it starts - how to fix

See also http://kb.mozillazine.org/Preferences_not_saved and How to fix preferences that won't save
How to set the home page - Firefox supports multiple home pages separated by '|' symbols

Hello,

to resolve this problem pelease got to %appdata%/Mozilla/Firefox/Profiles/

then open default folder profile look for sessionstore.js open it with notepad and then remove this:

{"url":"http://www.mozilla.org/en-US/firefox/11.0/firstrun/","title":"Welcome to Firefox","ID":1,"docshellID":7,"docIdentifier":1,"formdata":{"#country":233},"scroll":"0,0"}

save your file and restart firefox and it will work (ISA).

tested on firefox 11.0