build game crashes randomly since I change unity4.3 to 4.6.5

hi there I recently change my unity version from 4.3 to 4.6.5 and I didn't notice that my game is crashing randomly after testing in some levels. there is no error in my console, no crash in editor even after built game crashes no log file produced. I tried: 1. Autoconnect profiler 2. development build and not 3. X86 , X86_64 4. delete Library folder and reimport project in 4.6.5 and 4.6.2

at the time game crashes nothing happens just sounds continue playing and screen freezes and no input works.I didn't have this issue with unity4.3.

any advice on how I can find this issue? thanks