This has been happening to me, too.
I've been trying to load Pleasantview, and it just stops working. I get the little notification window telling me that SimPE has stopped responding.
I have windows Vista, and I'm assuming that I already have .NET 2.0.
I've run a system check, and it's telling me that it can't find the Sims 2 University Folder...I checked, and as far as I can tell, it's where it should be.
What could the problem be?