Does Firefox always close for you when you want it to?

[mb]

For the longest time, whenever I close Firefox, whether I click the X, hit ALT-F4, or File -> Exit, firefox.exe actually only stops about 50% of the time. If it doesn't close, then the next time I want to open it, I have to close it via the Task Manager.
It even does it after a fresh Windows install and fresh Firefox install.. I just don't get it. Is anyone else having a similar problem? Any solutions?
And yes I am using 1.0.4. It's been doing it since 1.0 though.. I've pretty much just learned to live with it.

 

[JTalbain]

yeah i get this sometimes. firefox will remain as a running process in task manager. ive yet to find a solution to this issue.

 

[xcript]

Several extensions I've used have caused this behaviour.

 

[MobiusPizza]

Well it does stay for a while. But it usually closes after few seconds

 

[Mem]

I had this problem and also an odd 100% s CPU usage now and then which I could never find the cause,yes I ran all my anti-spyware and anti-virus software even tried few online ones as well to be sure,in the end I have gone back to good old Opera ,I must say new 8. version is excellent and is way better then Firefox IMHO.