I have a 2950 with the same issue. Did you ever locate a solution for this problem. We have 2 Telephone interface cards installed in our 2950. One is a Sangoma 4 Port Analog (FXO) card. The other is a one port PRI (T1) Interface.
Thanks for te reply. Never had only 1 card installed -- will check that out and get back here. FYI - this message stopped appearing for a while, not sure exactly how long. I just noticed it again yesterday.