Windows/SQL Login

Here's the scenario:

I have a client machine that's on a different subnet (10.0.4.x) than the SQL
server (10.0.0.x) which is configure for both Windows and SQL security.

If I log into that client remotely as the domain administrator, the ODBC
connection will successfully connect using both the domain administrator's
identity as well as the SA credentials. However, if I log into the same
computer using a non-administrative user's credentials, the ODBC connection
will not connect using either the user's credentials or the SA credentials.

Can anyone tell me why?

Thanks.

Ross