Hmm I see your concern Paul. So are you saying that the logic can be developed on machine A but not on machine B? Or that even if the logic is developed on machine A it won't run on B? Or that the logic that ran well in v5 on both machines now won't run in v6 on B?
I guess try and find out if there is something different about that machine too, Tabprocgrowth maybe, IE version, OS version?