If firefox starts with a blank screen (no buttons, whatever), then the one single profile you're using is screwed up. Typically FireFox 3 will mangle its fancy new bookmarks database.
You can work around this by simply running a second firefox on that machine. A new profile will be picked and you can close window with the non-working one.
You can fix the problem by quitting the damaged firefox and then typing
'firefox' in an xterm. The command will print something like 'exec
firefox -no-remote -P AdaqUserXX'. IF the firefox that opens is
still damaged, then 'AdaqUserXX' is the damaged profile. Quit firefox,
and run this command:
cp $HOME/.mozilla/firefox/adaquser.template/* $HOME/.mozilla/firefox/*.AdaqUserXX/