If it was a regular web-app game over wifi then you can try blocking pop-ups. I presume it's the same on the ipod touch as the iphone:http://docs.info.apple.com/article.html?artnum=305894
If this was a game bought from the online store, you should report it to Apple with steps to reproduce the problem.
If this is a game from installer.app on a jailbroken ipod, then you can't prevent them accessing these games.
There are parental controls in firmware 2.0:http://www.appleinsider.com/articles...alculator.html
so you could upgrade to it if it hasn't already been enabled and prevent running this game or visiting particular sites.