Re-sign APK to prevent updating - crashes "divide by zero"
Dude, just tell Google Play not to automatically update the application.

Given that this is a banking app, I would be VERY surprised if there was not some kind of anti-tamper mechanism in place, and this could be a part of it. Of course, this could have been a basic coding screw-up too. From the information you provide, we simply do now know.

Apktool might give you more information as to what is going wrong.