Whenever playing Flash games online (and Java games, too), my computer will shut down in that crashy sort of way (meaning instantly, no prompt, message, or blue screen) after 30 minutes to 2 hours of use. Then it won't start back up again for a while, between 20 seconds and 5 minutes. I check the event log and, right at the time of the crash, there's an error with IPNATHLP saying "The DHCP allocator has disabled itself on (my IP address) because it is outside of the ***.***.***.*** - ***.***.***.*** scope." and some troubleshooting options. What's causing it?