Weird problem with Chrome on not working with Vorple's "wait for any key"

I have a Vorple game on, and three testers have reported that “wait for any key” doesn’t work for them – they press a key but nothing happens. All are using Chrome. Weirdly, there are a few "wait for any key"s in the game, and the first one seems to work properly. The second one doesn’t always fail, either, just most of the time.

I’m not sure if this is a Chrome problem, or an problem, or a Vorple problem (everything works fine in Firefox, as far as I can tell).

(Juhana, thanks for Vorple, by the way, I really like it; and I know what a pain it must be to get everything working just right across all the different browsers!)