...and the app you tried to run did not launch? There shouldn't be a difference in OS for that code (for Vista-8) but I've seen funkier things on Vista and typically I don't test on Vista at all. I'll try to check that out and see what the deal is; even if it fails I'm thinking you shouldn't get the Interactive prompt - that may be something I can fix if nothing else!
EDIT: ETS v1.1 is working on my Vista VM (which doesn't work very well to begin with, it's Vista...) so I wonder if it is the particular Vista you were running on with something quirky about it or what. Let me know if you continue to have these problems, also note if it is always the same software you are launching via ETS that exhibits the issue and if, say, launching something arbitrary like notepad.exe would work just fine on the affected machine.