If not, what word do I mean to use when I use "show-stopper" negatively?
It seems that in high-tech culture a show-stopper is a development problem that prevents forward progress, or an unacceptable outcome. (At least in a non-english-speaking high-tech culture.)
My wife called me on it this morning when I used show-stopper in this context.
When I stopped to think about it, I couldn't think of the word or phrase I should be using that I seem to have confused with show-stopper.