bwells

I'm having a weird problem with transfering calls. The PBX is an M1000 w/succession 4.0. The problem only happens with DID calls. If the call is transferred to another extension, but nobody answers, it will not fwd to voice mail. The switch thinks its fwd'd to voice mail, but the caller just keeps hearing ring back tone. We can transfer inside ext. to ext. calls and they work fine, this is only with DID's. When we tried to trace the call, we can see everything that happens up untill the PBX tries to send to voice mail. Then the trace shows nothing. If a DID call comes in and nobody answers, then the call routes to voice mail after 4 rings, like it should. The problem only appears when a transfer is involved. Note that the voice mail is at a different PBX that is connected to the problem PBX via tie T-1's.
We also tried transferring a DID call to an ext. on a remote 11c. This worked fine and eventually went to voice mail after 4 rings like it should. As far as we can tell the problem is a PBX wide issue related to this one PBX only. But we can't find the issue that would seem to block DID calls from being transferred to another extension and then fwd to voice mail.