Since a recent Norton Internet Security program update by Symantec it now keeps enabling Intrusion Prevention although it has never been disabled. The result is that when I come back to the computer Firefox 3.0.10 has the message that it had to close unexpectedly and re-start.
I suspect that every time NIS tries to enable an already enabled NIS 1.0 Add On it has to close Firefox to register this 'change'.
I have checked the history each day and the record for this event coincides with the time that Firefox has been closed down.
It is getting very annoying finding Firefox has been closed without notification.