NetMeeting Connection

Just recently when I use NetMeeting from home to call my office computer, it won’t accept my username and password, and after three attempts tells me it won’t accept the call. I can, however, use NetMeeting from home to call the server and other workstations in the office. Another point is that from inside the office I can use NetMeeting to connect to my office computer. All workstations at the office are W2k SP4. Thanks in advance.