Escape does not end experiment

I recently made an experiment in Superlab 4.0. The experiment runs fine, but when I hit “Escape” to end it (the task is timed so some people don’t finish), nothing happens - it keeps running. It’s not the “Escape” button itself, as it works on other programs. I’m running this on a Vista machine - not sure if that’s related. Any help ASAP would be appreciated!

What’s going on in the experiment when it’s ignored (e.g. waiting for input, ISI, playing movie, etc…)? Are other keypresses working correctly?