There is no way on earth that demigod uses 1mb of bandwidth. I'd guess it uses at most 0.05-0.1mb, even then that's a stratch since everyone runs their own sim so the only bandwith you are going to use is for location and action updates. It should use more like 0.01mb.
What's more likely happening is either:
1) your school implimented a new throttling/sharing setup and someone in your dorm is wtfpwning the torrents (unlikely that this would kill your connection unless they are throttling by building instead of IP which would be retarded) or
2) there is a bad router someplace or
3) you have a trojan and someone is running a porn server out of your box
To test 2/3 download a traceroute program that lets you log activity and run it for 24 hours. Maybe ping lagwars vent (although i read something was wrong with that recently) so just ping someone who plays dg (like pacov!).
If you can't figure out what the traceroute means post it here.