No audio on inbound calls

This problem started occuring out of nowhere. Outbound calls are fine. Both sides of the conversation can be heard fine. When I dial the asterisk box, the IVR is supposed to play a greeting using background and wait for a response, except we don’t hear anything. We have a single T1 PRI (Wildcard TE122).

Here’s the CLI:
Accepting call from ‘786*******’ to ‘305*******’ on channel 0/1, span 1
– Executing [305*******@all-incoming:1] Goto(“Zap/1-1”, “TRCIVR|s|1”) in new stack
– Goto (TRCIVR,s,1)
– Executing [s@TRCIVR:1] BackGround(“Zap/1-1”, “silence/1”) in new stack
– <Zap/1-1> Playing ‘silence/1’ (language ‘en’)
– Executing [s@TRCIVR:2] Goto(“Zap/1-1”, “TRCOperatingHours|s|1”) in new stack
– Goto (TRCOperatingHours,s,1)
– Executing [s@TRCOperatingHours:1] BackGround(“Zap/1-1”, “company/trc_operating_hours”) in new stack
– <Zap/1-1> Playing ‘company/trc_operating_hours’ (language ‘en’)
– Channel 0/1, span 1 got hangup request, cause 16 - I hung up the phone at this point.
== Spawn extension (TRCOperatingHours, s, 1) exited non-zero on ‘Zap/1-1’
[Feb 16 20:16:18] DEBUG[6507]: chan_zap.c:2972 zt_setoption: Set option AUDIO MODE, value: ON(1) on Zap/1-1
[Feb 16 20:16:18] DEBUG[6507]: chan_zap.c:2611 zt_hangup: Not yet hungup… Calling hangup once with icause, and clearing call
[Feb 16 20:16:18] DEBUG[6507]: chan_zap.c:2968 zt_setoption: Set option AUDIO MODE, value: OFF(0) on Zap/1-1
– Hungup ‘Zap/1-1’

Any ideas on how to troubleshoot this problem? The carrier came back and said everything was fine on their end.

Thanks.

The version of Asterisk is Asterisk 1.4.18 on Slackware 12.0.0