Something passed an out of range step index to a call to retrieve a step.
http://www.kinook.com/VisBuildPro/Ma...emproperty.htm
VBP itself uses the object model, so it's possible that the problem is with VBP itself, although we have not encountered or heard of this error before now, so we would need more info to investigate. Script code in a Run Script step or script expression could also be calling the object model.
http://www.kinook.com/VisBuildPro/Manual/script.htm