Pogo and Slingo freeze when using router...?

I have 3 computers in my home connected to a Belkin router. Two of the computers are wired directly into the router, and one is on a wireless connection. Any time any of the computers try to play Pogo or Slingo or any Java based game, I can play for a few minutes then the game freezes. However, if I connect the computer directly to the modem, it works just fine. We have changed routers, modems, network cables, and nothing seems to work. Any suggestions???