Stimmer, holy moly, you are GOOD. You are absolutely correct -- I will change score to be an unsigned long!!!
I chose unsigned int before I added the free life every 10000 points feature, so I didn't think anyone would roll it over -- thanks for the stress test.
UPDATE: the unsigned int won't roll over to 0 until 65535. My bug is that I'm displaying the unsigned int as an int. I used %d instead of %u in the call to sprintf.