Ok - this is kind of a weird one. I have a login button which, upon an invalid login produces a JDialog informing the user of the invalid login. The JDialog has been setModal(true). What I've found is that if the user clicks the button multiple times quickly (like, for instance, if they double-click instead of just single-click), I get multiple dialog boxes. I've tried disabling the login button as soon as it's clicked & disposing the dialog before creating it, but it doesn't seem to help.