Apps won't open on my itouch?

When i sync my itunes and my itouch, the apps i downloaded wont work anymore?

• i downloaded apps from the app store on my itouch earlier and they worked fine. but then i plugged my touch into my comp and it synced with my itunes. on itunes it says it has those apps on it now, and theyre still seen on my itouch's main screen, but when i try to use one of the apps i downloaded, it will start up but then close right away. can somebody help please =] thanks

• Answer:

  if you did the jailbreak thing with your itouch then the apps wont download properly anymore. that might be it, if not try deleting the apps then re downloading them.