I find that whenever I have been viewing news videos or similar and then want to exit the browser, although it seems to switch out, then if I later want to re-enter I cannot. I find that if I press Alt, Ctrl and Del, Firefox is still hanging and won't end or restart the program unless I go for reboot. This has now happened quite a few times. This can sometimes also happen if I have been downloading or listening to web audio files.

Incidentally this doesn't happen in IE and sometimes I switch back to this to continue surfing without rebooting. Any ideas?

I tried listening to the radio on the BBC site but can't reproduce that fault. What audio player is being used to play audio files?

After Firefox appears to have shut down (but really hasn't), can you see the audio player listed in the Running Processes as well as Firefox? If so, maybe it's something to do with that not closing down that is affecting Firefox.

Are you using the latest version of Firefox (0.9.3)? If not, you could try uninstalling your present version and upgrading.

Have now upgraded to version 0.9.3 and will see if this still happens. I think it is something to do with uncompleted tasks, ie searching for video or audio files which don't cancel on request.