How about posting the IP, subnet mask, and default gateway for the PC and both sides of each router? It looks like there would be problems getting traffic from a 192.168.1.2xx IP to a 192.168.1.1xx IP on another subnet if you used the typical 255.255.255.0 subnet mask. I'm not sure how that would cause it to work and then stop, though.

Also, unless you reverse them, I don't see the point in doing this. Traffic from your unsecured network will just be another node on your secured LAN. Aside from issues related to NAT, hosts on the unsecured network will have the same connectivity to the hosts on your secured network as if they were also directly on the secured network.