browser still running

Hi my browser ie or firefox runs in task manager even after closing down. each one uses up 50% cpu and loads of mem.each time I open up browser a new one appears in task manager.Once I get to 3 browsers running the sys freezes as no more cpu left.
Why wont it close when I shut down internet browser?
Only way to stop it running is to force it to close in task manager!
help needed guys
recent suggestion was comodo causing issues. so have uninstalled and now it is ok.
How can I run comodo without causing this issue?

I presume you have Safesurf install please uninstall.