Hi Mark,
QWP 5.4 introduced a feature that blocks the users to performe double savings (hit save button twice).
Also QWP blocks the save action when the validation on the page fails.
What you can do is to have create a custom action (using the sample code that we provide with QWP) and perform validations there or to use Form Component Behavior to perform validations.
What's your QWP version?
Thanks,