Pressing the button below will freeze my front end. An unpainted white dialog box comes up, then it completely freezes, and I need to forcibly kill the front end. CPU usage stays at zero during this.

Button["Ask", If[ChoiceDialog["OK?"], Print["OK!"]]]

Why does this happen?

What is the proper way to ask for confirmation before an action?

Answers:

My first question has been answered below and in the comment by @JohnFultz: use Button[..., Method -> "Queued"]. But this will make a button which doesn't work while evaluations are ongoing.

I need a button which works even during evaluations. I came up with the following solution:

Button["Ask", 
 CreateDialog[
  Column[{"OK?", 
    ChoiceButtons[{"OK"}, {Print["OK!"]; DialogReturn[]}]}]]]

CreateDialog returns immediately without waiting for an input, so the front end is not blocked. The functionality is moved completely into the dialog's button.

You can test that the button works and reacts immediately even while Pause[10] is evaluating.