(by the way, I have no hacks/mods/dowloads/or third party content of any kind--100% vanilla maxis game here)
Thats the problem. A clean game doesnt mean a "safe game." You need to "awesomize" your game to avoid conflicts like this. There are so many bugs in the Sims 2 and it doesnt matter if you have patches installed or not. Its probably too late to actually recover from this, but if you were to start over, it would be a safer experience if you used "awesome hacks."