Trouble holding a wireless connection

Hi.  This problem seems similar to a lot of other ones out there, but I haven't come accross anything that fixes it yet.  I just got a Dell Inspiron 1520 with a Dell Wireless 1390 802.11g Mini-Card.  I downloaded and updated all of the drivers.

The problem is:  after startup or sleep, the connect to a network dialog shows no networks.  If I reinstall the drivers, or change settings on the wireless router, or otherwise reboot the router, it finds the networks no problem and connects to the internet.  5-10 minutes later, the connection is drops to limited or no connectivity, and then kicks me off.  I can then go through the whole process again and be surfing for another few minutes. 

I've tried updates, power cycling the system, changing router settings, and everything else I can think of, but nothing is working.

Please help!