Symptom:
Dial-in users may hear garbled audio when they join a channel which is participating in a VTG.  The problem seems to depends on several factors:
1) The VTG needs to contain a mixture of G.711 and G.729 channels or radios.  
2) Some end-points are M-IDC, and others are R-IDC.
3) The source and destination talk line.

Some talkers can be heard clearly, whereas other cannot, depending on the permutation of these variables.

Conditions:
IPICS Dispatch Console 4.8(1)