Sims 3 won't start up?

The launch menu will open, but when I select "play," it says the program won't respond, and it never does respond. I've let it sit for hours. In addition, it won't even let me close it using ctrl+alt+del. My OS is Windows Vista (yuck!), but does meet the system requirements. I have all the major expansion packs (meaning all except the ones that only give more items and hair-dos, etc), and didn't start experiencing problems until installing Generations. I was able to play it last night after installing, but today, it won't run. I've tried uninstalling and reinstalling and restarting my computer. Any ideas?