TCP/IP problems

["Bryan K. Walton" <walton@berbee.com>]

First, I would like to thank everybody who offered advice to me yesterday
regarding why iplogger was crashing my computer.  I got that fixed, thank
you.  Now, (let me preface what I am about to say by adding that I am
teaching myself linux by getting Debian running on my Thinkpad.
Therefore, many stupid learning mistakes. . .) since yesterday, I have
rebuilt my machine after successfully screwing up my libraries.  My
computer is connected in a networked office environment using DHCP.  My
IBM Thinkpad 390E is using a Xircom REalport card (which it recognizes
fine).  I have a DHCP client on my computer, and when I start it up, it
gives me back an IP address.  However, I cannot generate any further
outgoing or incoming traffic.  When I open up my browser, I can't browse
web pages via domain names or IP addresses.  I can't FTP anywhere, or do
anything else.  This sounds like a TCP/IP problem.  Thing is, I have no
ideas for how to fix the problem, or even to verify it.  Any advice?
THANKS!

Bryan