I got a message when i opened firefox about which profile to use, i tryed to select default but it told me it was in use or somthing so i had to select Default user (thats a different profile btw)

This has happened before and i forgot how i got mine back, So my question is... How do you change profiles in firefox? I cant see an option anywhere, and its not documented in the help files.

you run it with a command line option  like

firefox.exe -profile

or something

more details at mozillaZine

To get all profiles unlocked, go to:
C:\Documents and Settings\<username>\Application Data\Mozilla\Firefox\Profiles
(for non-XP machines, vary accordingly)
then go into each profile folder with Firefox fully closed and delete any lock files. I can't give you the name of the one to delete, as my Firefox is set up slightly differently, so it only uses one profile.

On Linux, the file is '.lock', whether that helps at all.

Thanks Raceprouk Your suggestion worked. Thanks dempsey for yours too.

this happends to me when firefox hangs..
hit ctl alt del, and you'll probably see two firefox.exe's running.. end both process and start firefox up again.. it'll work normally.
cause what happends is that your profile is running on the 'hanged' firefox and it needs to load another profile.. so ya..