Troubleshooting one user who can login without a problem, and the client reads the contacts from the CUPS server, but it will only allow him to be in 'Offline' status. Also, he cannot see anyone else's status, and hence cannot IM anyone. However, when he is logged in, others show him as available. He can also use the softphone to recieve and place calls.
There are no problems reported in Server Health. I have verified that his CUCM username matches his AD username. This occurs wherever he logs in (on different clients), but doesn't if he logs into a different CUPS server (different domain). The only clue I can see is a packet I am seeing about a malformed SIP packet during subscription while I was packet-sniffing. Has anyone seen or heard of anything like this?