After upgrading to Skype 188.8.131.520... it randomly crashes (I mean just Skype... I just suddenly hear that Skype is logging out..randomly, AFAIK it crashes..)... BUT WHY?? I can revert to an older version of Skype... My phone is a LG GT540..
There is no way to know for sure unless you view logcat. Use adb which comes with Android SDK and execute the command logcat.
I usually do the following steps to find out what causes an application to crash:
Enable USB debugging (Settings -> Developer Options -> USB debugging)
Plug in USB cable to your phone and connect it to your machine.
Run adb logcat
Run the application and try to make it crash while viewing the logcat.