I got your example to work when I'm physically on the server, but when I try it from my workstation, I get:

An error occurred while preparing the query "SELECT * FROM 'LDAP://NOVMDC02.SD.INT' where objectClass = 'User' " for execution against OLE DB provider "ADsDSOObject" for linked server "(null)".

I assume it's some sort of security issue.

Any and all ideas are welcome.