Microsoft Office Communicator

I am a PFC in the army and do Network Administration and troubleshooting. I recently installed Microsoft Office Communicator on a machine. The person that will be using the program logs in and then it ask for a username and password. This does not seem right because when I put in my email address to log in it comes up no problem. We tried changing is account, using a different military email and it still only did it to him. Myself and my supervisor can both log into the program with out any problems. Any suggestions on what the issue might be?