Photoshop Elements: Vanishing dialog box(es)

Been using PE a very long time; started with version 1, moved to 3, am now using 6 -- contentedly, except...have a "missing dialog box" problem. Recently, dragged Unsharp Mask box toward edge of window (as I've done many times), to view more of photo; it bounced out of sight, disappeared from PE window and could not be found. I shrunk the window, minimized the window, shut down everything else. No dialog box -- although it remained active, applying whatever default values were last entered (when the box was last visible). If I hit the Enter key, it would apply the values and (apparently) close the box. If I hit Escape, it would close the box without entering the values. So I closed down PE and re-opened it. Problem persisted. I rebooted; no difference. Finally, I removed PE6 entirely, and reinstalled the program. That worked. Today, the same thing happened with a Levels adjustment layer box. Now, ALL the adjustment layer dialog boxes can be opened but not seen. This never happened in all the years I've been using PE; now, it's happened twice within a couple of months. Do I have to re-install again? Where've they gone? Anyone else encounter this? Is there a solution short of re-installing and having to reset all my preferences, etc., again. Thank you.