Firefox 1.5 makes only troubles

Hi,

till now I regret updating from 1.0.6 to 1.5 it only brings problems like:
I can't start Firefox anymore, I get the msg 'Firefox is already running,
but is not responding. To open a new window, you must first close the
existing Firefox process, or restart your system.'
I cannot find any running process and I restarted my Sys. no cange, what's
wrong?
Tank you!
-- 
chEErs roN

I'm root, I'm allowed to do this! ;)
keep on rockin'