Hi Denis,
I’ve got a problem that identical to yours. I have a Cisco AS5800, registered to a VocalTec VoIP network under VocalTec Gatekeeper. From AS5800, I made call to a VocalTec GW (VGW480), the call was connected but dropped after 15 seconds. The SS7 trace in PSTN side show me that the release cause is “Recovery on timer expiry”
. Please tell me what did you do with your Clarent and Cisco GW. I think it could help me to solve my problems