Apps get closed immediately after opened in iphone?

I have an iphone 4. Apps were working before i sync them on itunes. After synchronizing, apps which were downloaded and purchased can't be opened in iphone.
In itunes, there was an app 'idownloader'. I add some videos in it from my pc and sync it. Then whenever i try to open some of purchased apps, it closed immediately. Tell me, what to do now?

Buy a Windows Phone. Problem solved. Sell your iPhone and donete it all to whoever you want ;-)