1) Make sure you can see your network (Ex. Ping a server)

2) Try to create an ODBC connection  to a SQL Server on the network and test it.

3) Check the SQL Server Client Network Utility on your PC and make sure you have the proper protocols enabled (TCP/IP,    Named Pipes, etc)

4) Make sure that you have the correct port number for your SQL Server you are connecting to..If not create an entry in the SQL Server Client Network Utility for the server and correct port number.

Hope this helps

Jim