I bought a new high speed 4gb memory stick pro duo the other day and I put it in my PSP. It cant play anything! If I put in a UMD the memory stick doesn't let me play it. It can't play PS1 games off it as well. Maybe it's a virus on the memory stick that is now on my PSP. I know I got everything right because I have a different PSP memory stick that will let me play PS1 games and UMD's. Please help me!!!