iPhone stuck on startup screen, crashes iTunes when I connect

I'm running an original iPhone. I upgraded to v2 of the OS when it came out, and was running apps with no problems until today. Today I bought a couple of new apps. When I connected the phone to my Mac, it backed up, updated the apps, and ran fine for a while. Then I tried one of the new apps (Grocery List). It didn't run. I tried it again. It crashed my phone. I'm stuck on the startup screen (with the centered Apple logo). I've tried rebooting, but I can't get past this screen. iTunes runs fine on my Mac laptop until I connect the phone, at which time I get the spinning beachball. My phone is stuck on the startup screen, and is getting real hot.

Any suggestions? Thanks.