Network Troubles on Dell GL+ 5100

[JakeCatfox@aol.com]

Hi, I installed Debian on a Dell GL+ 5100, and I installed the module for the 
3c509 (3Com 509-based NIC card), and got "installation succeeded." ifconfig 
can find it as eth0 just fine, and I can ping my IP address and it works 
fine. But when I try to ping any OTHER devices on the network it fails! The 
OS finds the card just fine, but it can't be pinged or ping anything, or 
telnet to another machine, either. I even tried a different cable, plugging 
it into another Dell running WinBlows 98, and into a switch hooked up to a 
LAN.

Does anyone know what I'm doing wrong?

-- Deven G.