[cisco-voip] CM 4.1 to PBX GW troublshsooting

[bababooey at cox.net]

I have a Call Manager 4.1.3 and a router interface to a pbx with a T1 trunk.  It is configured for H.323.
I find that I must reset the T1 controller almost daily to restore the PBX access.  I believe the problem is on my side not the PBX, because PBX users can still ring ip phones on the Call Manager.

How do I begin to troubleshoot this problem?
Which debug would be helpful?

Thanks - 
Bob