Using Alt+F+C closes Firefox when it is only supposed to close the current tab

Hi,

I am using Kubuntu 6.10, Firefox 2.0.0.3. Firefox was installed using the Adept Manager. When I have multiple tabs open and use the key combination Alt+F+C to close the tab that is currently in focus Firefox sometimes closes completely. That key combo should only close the tab - not cause Firefox to shutdown. When I restart Firefox, a dialog appears asking me if I want to start fresh or restore the last session. This problem occurs intermittently - sometimes the key combo closes just the tab and other times it shuts Firefox down completely. It does not appear to make any difference what site(s) I am visiting.

Any ideas?

Thanks