When quickly dragging JInternalFrames around (such as the Internal Frame demo of SwingSet2), they get "stuck" in the lower right part of the containing pane. They can only be dragged back to the upper-right if it's done very slowly. Pretty strange, but also pretty serious. This does not happen with Mantis b02, but does happen with the Mantis workspace after the latest Swing integration. The problem happens on Linux, Windows, and Solaris.