I have been seeing a problem that tunrs logins from a trusted domain into SIDs in a local windows group.
Whan I add a login from domain "PROD" to let say the Administrators group on a server in domain "TEST" (TEST trust PROD) the login will change to a SID (i.e. "PROD\username" becomes "S-1-5-32-1045337234-12924708993-5683276719-19000". Also rebooting a server that does not have this problem will sometimes turn all the existing users in local groups into SIDs except for the ones that have RDP'd onto the server at some point (i.e. server admins).
This is not persistent and sometimes gets fixed with a reboot.
We have a mix of 2003 and 2008 DCs.
I'm not the domain admin.