Report the MD5 signature in the stderr output as well so that duplicate screen shots can be quickly identified. Of course this assumes that the exact same PNG is generated across different machine types and video cards. Currently I believe that it should given the hardware in question is virtualized.
Before COM, polling for the current state wasn't as critical. If the poll operation failed, we would try again in one second anyway.
After COM, it is used as a test to see if the communication channel between the wrapper and VirtualBox is still operational. If not, temp exit and hope things work the next attempt.
Rom Walton