Scenario:

• VMware with Windows 2003 Server and Team Foundation Server (TFS) 2008. No Windows domain membership, just a stand-alone workgroup server.
• Connecting from a client in a different AD domain with my own TFS API wrapper or with the „tf.exe“ command line tool to the server.

Error:

TF30063: You are not authorized to access server <servername>

I received the above error message all the time, even when providing a valid user name and password for the server.

Solution:

Seems that the credentials still depend somehow on the logged in user. I therefore created a new user on the TFS that has the same user name and the same password as my currently logged in workstation user.

After that, everything worked. See also this somewhat related blog posting.