>>oUser = GETOBJECT("WinNT://SOMEDOMAIN/someusername,User")

>I tried this, and there was about a 20 second delay before it found the groups. I suspect it was searching the network for other servers in the domain (I used a server name for SOMEDOMAIN, was this OK?) before it returned an answer. Subsequent requests were nearly instantaneous.

You can narrow the search for the computer by qualifying it with a domain or workgroup:

oUser = GETOBJECT("WinNT://MYDOMAIN/MYCOMPUTER/someusername,User")