I'm sorry Zap! I have no idea what happened to your game.
This has nothing to do with your specific problem, but my game was lagging, freezing, bugging and crushing like crazy. For other non-Sims-related reasons I installed a program called CCleaner, ran it... and found 850 (yes, 850!!) registry errors in my computer. To my surprise, around a half were from The Sims' registry entries. That was probably due to incorrect/failed un- and re-installs. Anyways, I told the program to fix it all and now my game runs much better! I've never experienced this specific bug (or whatever it is) but I did have some very strange things happen in my game that don't happen anymore, so you might want to check it out.
Just a note in case you decide to do it: make sure you do the registry back up the program asks you to do! I've used many registry cleaning programs before and never had an issue with deleting the wrong files, but I've read it could happen so it's good to have the back up. And it's always good to check what the program found before you click on the "clean" button, just in case.