We're using Windows authentication and I've tried all sorts of permutations for setting up an ODBC connection. In management studio there is a user listed (with permissions to our databases) labeled as tulip\CTAP_Professionals. There's no separate user for tulip\ctap. I was assuming the having membership in the group CTAP_Professionals on tulip would give users permission to connect to the database, but apparently the only member of that group able to gain access is the general user "ctap".