Here is a fun one. On Mac OS X when you are using the following JVM option dragging the scroll bar or resizing split panes will move the entire window.
This does not happen in the main window but on subsequent dialogs. I noticed this first when scrolling in the settings dialog. It would seem this is due to the native window's need to support movement via any point on the window as opposed to the traditional Mac way of dragging from the title bar to move the window. I really hate the brushed metal windows.
Mac OS X 10.3.2
I didn't initially find this one in the tracker but perhaps my search skill are lacking.