Like most of the addicts, the moment the new iPhone software came out I upgraded. There were a few apps I was curious to get my hands on from the new AppStore and some others that I'd blow some of my birthday money on as fun-to-have stuff.
Cool. It's been working great. I pulled down Chopper and Things from the AppStore via my iPhone (this is the old one, not the 3G) and started playing. Cool. That was a few days back now.
Today, all my apps stopped working. Not a crash, but clicking on any of my apps resulted in being booted back to the application menu. All iPhone native apps worked fine. WTF?
After some googling I found the answer, but first, the why: Yesterday I downloaded my first App via iTunes and sync'd it. It worked fine, until I sync'd all my apps today. So what happened?
Nothing, as it turns out. I was trying all kinds of crazy things, rebooting my iPhone, reinstalling my apps, etc. Nope - that wasn't it. All you need to do is bring up iTunes, click into the Applications folder and Double click on one of the Apps you downloaded on your iPhone. When it asks for your password, do so, and you'll be authorized. Your next Sync will fix things up.
You shouldn't have to remove/reinstall the apps. I had already, so I can't be 100% sure, but what I read said you should be good.