If possible contact TAC. I had the same problem w/ the same setup, however they were all private lines. Turned out to be a bug on the VWIC-2MFT-T1 cards that was fixed in a newer IOS release - 12.4(5) Advanced Security. I believe I was running 12.4(3a) or so to start with and the private lines were constantly flapping, of course the telco tested clean and was actually telling the truth for once! :) Can you post a show controllers and show interfaces? Clear your counters and wait 15 min.