It may be a setting with your graphics card. See:
LW loading blank and how i fixed it. Change graphic card settings to program controlled or AA. 3D settings.
If that fails, try uninstalling java from the add/remove programs. Then reinstall the latest version(JRE) using the offline installer from here:
http://java.sun.com/javase/downloads/index_jdk5.jsp
If your using a mac, try changing skins to black or metal.