hmm..interesting...
Assuming there is no other device in between CCM and 2911 that could be
messing things up?
Do u have a mgcp bind on GW for voice vlan interface?
What is the GW's IP that u see for the fxo port on the CCM?
If u can, upload GW config, sh mgcp end, sh ccm-man, sh mgcp
along with a screen shot the fxo from the ccm.
IOS and CCM s/w ver ?