If you have installed the latest IE7 and use Outlook and McAffe Virus Scan, you may have noticed your Outlook mail client locking up quite often.
Seems that during normal operation IE7 is throwing buffer overflows, or doing something that looks like a buffer overflow (quack quack). This triggers McAffe Virus Scan which promptly kills the running thread.
Eventually Outlook gets deadlocked and freezes and you have no choice but to kill it and wait happily as it rebuilds your local mail cache.
Oh what fun.