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Router closes TCP connection after 30 minutes

I have recently replaced my D-Link DIR-100 router with a Cisco Linksys RV042, but unfortunately there seems to be a problem with it.

I have an external TCP connection coming in to a local service, and I therefore set up the router to redirect the incoming connection for the given port to the local PC hosting the service. This worked perfectly. I also opened the Firewall access rules to allow all data from WAN2 to be propagated through. This also worked just fine, and I can connect from the internet to the local PC, just like I could with my old router. Unfortunately this is where the simularities stop. When there is no communication on the TCP connection for more than 30 minutes then the router closes the connection automatically. This is NOT what I want. I only communicate on the TCP connection very rarely, but I do not want it closed automatically - at least not after just 30 minutes.

I did some research on line and it appears that there in some routers are a TCP connection timeout, which in the router I read about, defaulted to 1 day. This would be OK. I experimented and found that if there is communication every 30 minutes then it is not close the connection, but if there is 50minutes between communication then it closes the connection.

As I read that this timeout has to do with security I experimented with the firewall and found the following:

1. Disabling the entire router firewall fixes the problem !!!

2. Disabling just DoS has no effect (problem still exists)

3. Disabling SPI means I cannot connect at all !!! (new and much worse problem)

4. Disabling Block WAN Requests has no effect (problem still exists)

Is there a way to solve this problem without disabling the entire firewall, as that is not what I want to do. I have the system set up for Dual WAN (load balancing), and I only want to allow connections to a handful of ports on the one WAN, and block the other WAN entirely.

P.S. I was referred to the Cisco Small Business Support Community by the Cisco Home community, so I hope this is the right place.

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