Tomato Shibby - TV Receiver loses connection after longer standby, need to restart my router

Hello,

I have a problem with my new TV receiver: It loses the connection if it is in longer standby and it's just working again after following process:

Turning Receiver off --> Restarting my Tomato router --> Turning receiver on

At first the IP of it was assigned with DHCP, then I assigned it manually.
This didn't helpt, I still have the same problem.

Then I tried to bound the IP to the MAC address, this also didn't work.

Could someone please help me? What am I able to do?