asterisk users - Aug 2011 - Can't use SmartVoip/JustVoip after update

I was using Asterisk with SmartVoip and JustVoip for a long time running 
on CentOS 5. Recently I upgraded to CentOS 6 with a fresh build of 
Asterisk 1.8.5.0 Using the same firewall and SIP configuration as before 
now I can't dial out:

retrans_pkt: Retransmission timeout reached on transmission ...
Packet timed out after 6400ms with no response
retrans_pkt: Hanging up call ... - no reply to our critical packet

Port 5060 UDP incoming from NET to FW is enabled and not forwarded, all 
outgoing ports are enabled to the NET.

I'm lost. Any idea, how to fix it?

Thanks... B?la