Calls interrupt because of Received REMOTE_RETRIEVAL

Some of my calls interrupts with the following error. May someone has an idea what causes this? MAy the remote party puts me on hold and the result is the following?

[2009-04-16 10:39:44] VERBOSE[27939] logger.c:     -- Zap/1-1 is proceeding passing it to SIP/14-0829eed0
[2009-04-16 10:39:46] VERBOSE[27939] logger.c:     -- Zap/1-1 is ringing
[2009-04-16 10:39:55] DEBUG[3117] chan_zap.c: No echo training requested
[2009-04-16 10:39:55] VERBOSE[27939] logger.c:     -- Zap/1-1 answered SIP/14-0829eed0
[2009-04-16 10:40:01] DEBUG[3117] chan_zap.c: Received REMOTE_HOLD notification on CPE channel. Not Starting MoH
[2009-04-16 10:40:01] VERBOSE[27939] logger.c:     -- Started music on hold, class 'default', on SIP/14-0829eed0
[2009-04-16 10:40:06] DEBUG[3117] chan_zap.c: Received REMOTE_RETRIEVAL notification on CPE channel.
[2009-04-16 10:40:06] VERBOSE[27939] logger.c:     -- Stopped music on hold on SIP/14-0829eed0
[2009-04-16 10:40:15] WARNING[3166] chan_sip.c: Maximum retries exceeded on transmission bba7bfe8dd9370e4 for seqno 24530 (Critical Response)
[2009-04-16 10:40:15] WARNING[3166] chan_sip.c: Hanging up call bba7bfe8dd9370e4 - no reply to our critical packet.
[2009-04-16 10:40:15] DEBUG[27939] chan_zap.c: Set option AUDIO MODE, value: ON(1) on Zap/1-1
[2009-04-16 10:40:15] DEBUG[27939] chan_zap.c: Not yet hungup...  Calling hangup once with icause, and clearing call
[2009-04-16 10:40:15] DEBUG[27939] chan_zap.c: Set option AUDIO MODE, value: OFF(0) on Zap/1-1
[2009-04-16 10:40:15] VERBOSE[27939] logger.c:     -- Hungup 'Zap/1-1'