I'm moving this to the TestLeft community forums here...
... but since TestLeft DOES do things similar to TestComplete, my guess is that it is one of two things.
1) A timing issue where you are attempting to interact with an object that hasn't been rendered or instantiated yet and, therefore, throw the error
2) An object identification issue where something used to identify the object in question has changed or is different on the different machines.
In looking over your stack trace, I'm aiming for option #1 here... it looks like you're attempting to click on a pop-up menu of another object... it's possible that the object in question hasn't been instatiated yet. AGain, I'm not very familiar with TestLeft but I would guess that there is a way to drop in a hardcoded delay before the error command to diagnose the problem. If that works, then... again, this is a guess, you might want to look at incorporating some sort of "Wait" methodology to wait for the desired object to be available before interacting with it.
