Problem with game center

[tjsilver]

Hello,

I'm an old fart and my computing knowledge is 100% Windows. Owning an iPad2 is my very first experience of iOS, so please forgive.

I downloaded the game Aki Mahjong (I'm addicted to it). However, for some reason the game no longer 'recognises' me. That is to say, when I win a game I have to manually enter my name. When I go to the game centre, the app thinks I was last online in September!

I've obviously changed a setting somewhere but have no idea what.

I have updated to iOS5

Any pointers much appreciated.

Tim