User Profiles Not Updating at Logoff

I am running NTSERVER 4 and about 20 NTWORKSTATIONS 4. I recently switched from workgroup to domain. All of them are using roaming profiles and their profiles are stored on the server. I thought when a user logged off that their profile would be updated. Only two of my accounts are updating. Is there anyway to get them to start updating again. Any help is very much appreciated.