From time to time, I ran into the following warning(errors) when I tried to remote desktop to one of our development box. Here is something I found to figure out who has left his connected connections on the desktop, maybe you can boot them out, if you have permission:
1. mstsc /v:00.00.00.00 /console
Replace 00.00.00.00 with your server's IP Address.
2. Start Terminal Services Manger (Administrative Tools -> Terminal Services Manager, or tsadmin.exe).
Here are some details.