asterisk users - Sep 2011 - WARNING[2209]: chan_sip.c:19667 handle_response_invite: just did sched_add waitid(3429468)

Hi All;

Asterisk version is: 1.8.5.0

But I see at the consol the following warning and really I did google but did
not understand if it is bug or related to settings:

[Sep 13 15:04:56] WARNING[2209]: chan_sip.c:19667 handle_response_invite: just
did sched_add waitid(3429468) for sip_reinvite_retry for dialog
3c581fa96f2b-53yysntgjmwb in handle_response_invite

But actually, we see some SNOM IP Phones has NR (Not Register) at the LCD, and
it is able to receive and originate calls !!

I was think if this is bug or if it is related to session expire .. but I am not
able to determine until now. Any help?

By the way: which paramter in the sip.conf can be used to determine the timeout
of the sip registration (so the IP Phone should send the registartion packet to
keepalive within this timeout, otherwise it will be considered not register)? Is
it the defaultexpiry or something else?

Also, the above warning, to what it could be related? Is it a bug?

Regards
Bilal