My network ->
Analog line on Cisco 1751 as H.323 gateway.
C2800 as gatekeeper.
CallManager 4.1 with Cisco 7970 telephone.
Receive a call on this line. At the 7970 place that call on Hold. Press Resume. You get no audio path and in about 1 minute you get fast busy.
1751 is 12.3(14)T3
C2800 is 12.4(2)T5
CallManager is 4.1(2)