Hey Dan,

You can ping the IP address from the client, correct? Have you tried connecting via Query Analyzer on the client? DSN's use ODBC, QA does also. There's no magic to a DSN, it's really just a way to keep your connect string external to the app. Also as far as connecting there is really no difference between system, user, and file DSN's. Are you using SQL or NT authentication? Have you run Profiler while you're testing to see what if anything is coming across? What kind of lag are you seeing when you ping/tracert? I would suspect a network issue more than a SQL issue. Only other thought is to install latest MDAC on one client and test.

Andy