I figured out what was happening - turned out to be a "series of unfortunate events".
We use Machine Name identification for our Named User CALs. I had my motherboard replaced last week so my MAC address changed and Server was not recognizing my machine. Since it didn't associate my machine with the assigned CAL info, it kicked me over to a Session CAL. The other user we were testing with turned out to be the only user to have been inadvertently removed from his Active Directory Security group and was being denied access due to a lack of privileges. The third had his file privileges set but his Named User license wasn't assigned yet, so he was pushed to a Session CAL. Today has been one long series of odd coincidences!