Dual Honed Network behind Firewall Help

I am still having some issues with my configuration. I am able to dial out now with no problem. Inbound calls, however, are internmittent. It looks like the system is losing registration to voip.ms server. Here is my configuration and was wondering if anyone would give me some input:

server with 2 network cards

eth0 w/ gateway

eth1 no gateway configured

dns and

All Ip phones register and are configured on the 192.168.147.x network

Sonicwall appliance is gateway

Could the dual honed network be the cause of the incoming call issue? Do I need to turn on routing services through webmin? Outbound calls work great and inbound calls work great only after I have made an outbound call.