Channels Don't Release upon "Bye" message from car

Hello All,
I have a situation in which my channels are not responding to the “Bye” message from my SIP provider (Qwest LD). Here is the configuration:

AsteriskNOW 1.02 (I know there is an AsteriskNOW forum but I believe this problem is related to Asterisk Core so I am posting here.)
Asterisk is connected via h.323 to an Avaya 8710 v3.1.4.
The call comes in to Asterisk via SIP from Qwest. Asterisk transcodes the call to h.323 g.711 to an Avaya trunk group. A vector is run which prompts the caller to enter their conference room number. The call then goes back to Asterisk via a second h.323 trunk and on to the proper MeetMe conference number. The reason we are using Avaya at all is for a centralized Call Detail Recording solution as we bill our departments back for usage. Eventually this will change as we are upgrading our CDR package to support multiple sources. But for now this is the configuration.
The problem comes in when a user disconnects from a conference. Qwest releases the session and sends a “bye” message but Asterisk does not acknowledge it. In the Asterisk Log I see “Don’t know how to indicate condition 18 on IP”. That’s the IP address to the first “Inbound” h.323 Avaya connection.
My trunk groups in Avaya have Disconnect Supervision set to yes for both in and out. Is there something in Asterisk that I need to set that is similar?
I hope this has been enough information to give some ideas. Any thoughts?
Thanks for all of the help!