asterisk users - Jan 2008 - Maximum retries/no reply to our critical packet

Hello All,

Got one customer and he is getting disconnection within 15 seconds when 
he tries to make outbound calls. Initially, it was working fine without 
any glitches... Other customers on the same system are working fine, its 
just with this customer only.

This is the error message thrown by Asterisk on the CLI: -

Jan 18 12:23:30 WARNING[30532]: chan_sip.c:1228 retrans_pkt: Maximum 
retries exceeded on transmission 20e5feaa-1d3d7ef1 at 192.168.1.2 for seqno 
102 (Critical Response)
Jan 18 12:23:30 WARNING[30532]: chan_sip.c:1245 retrans_pkt: Hanging up 
call 20e5feaa-1d3d7ef1 at 192.168.1.2 - no reply to our critical packet.

Customer can receive inbound calls without any disconnections, its just 
when he tries to make outbound calls.

All outbound calls are sent to Nextone SoftSwitch and default codec is 
G729a. Customer has Linksys SPA-2102 - firmware ver 3.3.6 and Asterisk 
version 1.2.18.

Thanking in advance...

Cheers,
Nitesh