The DBA verified the CONNECTION_TIMEOUT setting is set correctly. FYI: there are 50+ users connecting. I seem to be one of the few experiencing problems.

What is unusual is the coworker who can connect is even sharing the same cable modem connection as me (through the router). Both of my machines cannot connect with Win2K SP3. His machine is also Win2K but with SP1. All machines have Oracle 9.2 client.

Thanks for the response, Steven!