As I said, I can't reproduce the issue. All of my SIP URI outbound calls work. Are you running Incredible PBX 13-13 on CentOS 6 platform??
Try commenting out the following line and see if that helps. Not sure it won't break something else.
Code:exten => _.,n,Set(SIPDOMAIN=${DB(MyDomain/FQDN)})
Done, but it prevents disa calls from working again