[xmonad] xmonad & opera dialogs

Hi, I'm using xmonad 0.9 and have a little problem: The opera dialogs are often missized, e.g. the download dialog (where to save a file) is often over 5000 pixel wide. Or the dialog to enter the master password is often every small, so that you can't see the input box. I don't know if that is a problem that can be fixed. Maybe it's just bad luck that opera doesn't work together with xmonad. But maybe someone else had such a problem and know a fix/workaround. Regards, Felix