Connection consistently drops after a period of inactivity

I recently moved locations and relocated my Business Class service. I'm using the same wireless router and cables as with my old install, but the tech installed a new SMCD3G gateway (hardware v1.01 / firmware v3.1.6.54).

My setup:

- 1 static IP which is assigned to a wireless router (or a directly connected laptop while troubleshooting).

- Gateway has DHCP and firewall turned off, so it should be acting as a bridge.

What I am seeing:

- After several hours of not actively using the internet, when I attempt to use it again, it is unresponsive.

- It doesn't seem to make a difference whether I'm connected directly to the gateway with a laptop or through the wireless router.

- I can get a connection to the internet again by some combination of power cycling the gateway and unplugging/replugging the network cable to the wireless router (or laptop -- I haven't seen a difference).

- It then maintains a solid connection for hours of active use. However, as soon as I leave for a few hours or sleep, the disconnection happens again.

My thoughts:

- The wireless router is likely fine. It was operating normally at my previous location and I observe the same problems when connecting directly to the gateway with a laptop.

- The cable is likely fine. It was operating normally at my previous location and swapping it out for another cable did not make a difference.

- The gateway may have a problem.