Hi, Only thing I can think of is the games you are trying to run require an ios that you don't have. Have you tried a game that you know will run on 3.1 or that has worked on that version before?.What I would do is update the system menu to 4.1 4.1 is safe for a modchip and won't mess with region free.Doing that will give you most all ios to run newer games and old. Here's two posts from this site that may be of help to you.
If you figure out whats wrong please post back. I'm on the drivekey to and would like to know what the deal was.