You can try this for a quick fix.
Download stendhal client and start it with the following command line:
java -Dsun.java2d.pmoffscreen=false -Xmx200m -jar stendhal-XX.jaror with:
java -Dsun.java2d.opengl=true -Xmx200m -jar stendhal-XX.jar(XX is whichever stendhal you run with, maybe 0.58 or 0.61 ..)
We are sorry for the inconvenience.
This problem is caused by a glitch in X11 pixmap and alpha usage in combination with java runtime. We are working on a solution and will inform you when the issue is solved and this work around is not needed anymore.