ping to your SQL server, see whether you get any response.
if yes then
go to SQL Query Analyser provide your login and password and see if you get the timeout error
if you get then you can either
1. try IP address of server instead of its name. OR
2. In Client Network Utility add alias for your SQL OR
3. in your hosts file make an entry for the server OR
4. tell me whether its been resolved
Best Luck..
Nilesh