Navigate to the folder
C:\Users\<userid>\AppData\Roaming\Mozilla\Firefox\ Profiles\<randomname>.default
and delete the contents (copy them to a backup folder first to be safe)
..
Then relaunch Firefox. It should recreate the defaults. Once you have it
working, you can restore your saved settings one by one to see what breaks
it.
***
"Leo" <> wrote in message
news

73462B0-2976-4592-9E89-...
> am running vista 64 bit and using firefiox as my browser. Firefox asked me
> to upgrade to its most reent version 3.5.2 and now firefox will not open.
> I know others that are running it with 32 bit vista-is it possible tha my
> 64 bit version is the probem?