I’ve heard of the effects of code devices saving permanently onto a game cart, but it almost always involves data that is saveable in some form or fashion. I’m thinking that your cart has been tinkered with. If I’d played SimCity before I’d be able to give you a response with more confidence, but for now I’m going to have to second SLing’s question.

Edit due to ninja: Couldn’t somebody take a cart and replace the ROM with an edited one? I mean, if the filesize is the same, shouldn’t it run normally aside from any modifications a hacker may have made?

Zaphod, you’d probably need tools to hook the cart up to your system and check it with an unaltered game file or something. Unless there’s any other change in the game to possibly hint at someone editing it, I’m not sure of any other way.