I'm stumped and so is tech support

OK here's the deal.  Up until recently everything was going fine with my 600m with the 2100 pci card and 1184 wireless router.  I get internet through a college ethernet connection.  I would be connected to the router with an excellent signal the whole time, but I would lose the ability to browse the internet after about 5 minutes.  Reset the router, internet for 5 minutes, no more.  Connected to the router the whole time (can log in and change prefs etc.)  Problem is most likely with the router because I can connect with other networks just fine (not the wireless card) and plugging directly into the wall gives me a good, constant connection (not the connection).  Dell sends me a new router.  Same problem.  I called back and tech support is stumped.  I have no idea what to do now other than buy another brand of router since I now possess 2 Dell routers that drop the internet after about 5 minutes (also, plugging into the LAN does the same thing).  Any ideas from anyone?  I'm at a loss at what to do....