I am just reporting what I heard on the local news here in Norman -- I have no idea to its validity but I do know that the apartment complex where Moussaoui and his two roommates stayed won't say if Berg lived there.
There seems to be an overlap as they are reporting that Berg did not immediately leave Norman. Also one of Moussaoui's roommates was advised to go to Pakistan to join up with the Chechnen movement.
Local people are trying to connect Berg to the three guys, Moussaoui and his two roommates.
Do know if Berg had withdrawn from OU, his email account would have been killed immediately so he didn't withdraw, but he didn't return for the spring semester either which puts him in an overlap with Moussaoui. Heard rumors of a white kid being with Moussaoui and his two friends for a long time -- in fact, we used to see a white kid with the guy with the long beard who was Moussaoui's roommate around Norman but I cannot remember what he looked like.