[Asterisk-Users] How to avoid "Avoiding deadlock..."

[Joe]

An Asterisk box at customer site shows these messages pretty regularly. This
causes one way voice, the called party cannot hear the calling party.

Apr  7 11:59:44 WARNING[18406] channel.c: Avoided initial deadlock for
'0x817b790', 10 retries!
Apr  7 14:47:46 WARNING[18406] channel.c: Avoided initial deadlock for
'0x81a4380', 10 retries!
Apr  7 14:58:53 WARNING[18406] channel.c: Avoided initial deadlock for
'0x817b790', 10 retries!

This customer is running Cisco phones, and an IAX trunk top our PSTN GW. The
PSTN GW does not show any problems at all.

I would appreciate any input regarding this issue. I've seen several posts
recently, but no one seems to say what the root cause of this problem is.

Thanks in advance,
Joe