Windows 7 - FF 3.5.1 won't close every time

It doesn't happen all the time but it happens quite a lot.
I close FF using the X top RH corner,all looks good.
Go to reopen and nothing happens.
Start task manager and FF is not present in Applications but in processes firefox.exe is running.
I end ff.exe then start ff and it opens up to the tabs and screen i was viewing earlier when I shut down.
This only started with 3.5 and continued with 3.5.1
Your help would be appreciated.

What extensions and add-ons are you running? Any toolbars? Sometimes browsers do not close properly due to those things. I had the same problem with IE7. Steam didnt work so well until i uninstalled an annoying toolbar. Then IE7 closed just fine.

Just basic extensions no toolbars

Hi, just uninstall firefox using Revo uninstaller and reinstall it again. This should fix this problem.

this happened to me too in FF3. you have to wait for it to end its process automatically or kill it yourself. re-installing will SOMETIMES resolve it, but sometimes it won't. i guess it's worth a try.