A simple application that I wrote seems to have some refresh issues with Swing when running with Mustang (this problem doesn't happen with Tiger). It seems as if, when Swing needs to refresh, it uses an out-of-date buffer instead of calling the paintComponent() method.
To recreate the problem you need the two files I attached to the CR (a .jar file with the application and a .gz file which is the trace file the application will read).
Run it like this:
java -jar GCVis.jar spec.jack.trace.4.gz 1 100
When the window appears, press Start and you'll see the text "Marking Start" at the top-left. Do that a few times until the text "Compaction Start" appears at the to-left. Now, try to cause a refresh by moving another window in front of the application window or iconify / de-iconify the application window. In most cases, but not all, the refresh in the JPanel that has the graphics will be incorrect and the window will either be totally gray or pick up out-of-date contents (the labels at the top and buttons at the bottom seem to be refreshed correctly).
If I do the above with a Tiger release, then the window is refreshed correctly.
I have managed to recreate this on x86/Linux and a colleague (Peter Kessler) also recreated it on SPARC/Solaris and x86/Windows. We have hit this with recent Mustang builds (e.g., b80).