Strange iPod Touch problem ... with my solution

I installed some apps last night, but when I tried them today, some crashed and sent me stright back to the home page. Worst of all, even some of my existing apps having problem, like FAcebook. Ironically, not ALL apps have problem. So I started deleting those new apps, like FastFood. No luck. I rebooted my touch a few times. Again, no luck.

Finally I found a strange way to solved the problem: I went to the App store, and downloaded one new app. Suddenly problems gone away. VEry strange.