That happens ocassionally. According to open feint you need to turn off your router for 15 seconds. Then turn it back on when your ipod is in range. That will reset it. I have had to do that myself and it works.
I've had the same issue for a few days now, based in uk.... Never heard the reboot router solution before but I've tried it and it made no difference to the problem for me.....
Oh, and to add to what I've said, it's only happening with games where I'm using it for the first time, old games already set up with it it logs in and works fine