Need help fixing an absurdly slow network

Hi.
I live in a house with a total of 12 guys. Apparently there is one router and modem for internet access. It has been this way since August of 2007 and we have had no problems with our connection until recently. We can connect to the internet, but it is slow and sometimes doesn't work at all. I right click on the connection and 'repair' it doesn't really change much. The only way I can get the internet to act the way it should is by unplugging the router and turning off the modem for a while and then turning them back on. The internet works at a good speed for a few minutes then reverts back to crappy mode.

We have a Netgear router and Comcast cable internet. I don't understand why the internet was working so well for so long and then just died. I am thinking the router may be jacked up but I don't know for sure. I am coming here for help because you guys have helped me in the past and I know you won't take months to respond like our landlord. Thanks a lot!

- esuule