Firefox not closing

[scott]

I've had a problem with firefox lately. I close it and attempt to reopen 
it sometime later and get a message that firefox is already running. I 
have to do a "ps -e | grep firefox" to find the PID to kill it. It 
usually shows 2 instances of firefox running, one with a 'defunct' tag. 
I've renamed the .mozilla folder to .mozilla.old and it still happens, 
even with no extensions at all.

Any ideas?

Scott