The Sims games (since at least 2) tend to mess up your keyboard settings (if they are anything other than North American keyboard layout) after a few hours of gameplay. I notice this happens and suddenly I cannot find my ? or ' (which I tend to need during a chat or writing a description on an upload I want to send to the Gallery) and even after quitting the game, I cannot make it work right. I must reboot my computer to get my keyboard to work as a European keyboard.
Since I have suffered this problem ever since relocating to Europe, and it has persisted over multiple computers and multiple generations of the Sims, I do suspect it has something to do with the way they set up hotkeys.
I'm pretty sure there's no hope in triggering a response with the ALT GR key. Anything that requires that, you can check some of your other keys that you'd least expect and you'll eventually find it, but it wont always be that one because EA isn't very good at thinking about things that effect users.