After upgrading to JDK 6 Update 12 (1.6.0_12), Performance Monitor does not display any applications in the Applications window. This issue appears when any application on the system is running JDK 6 Update 12, even if Performance Monitor is running JDK 6 Update 11 or earlier.
Workaround: Uninstall JDK 6 Update 12, reverting back to JDK 6 Update 11 (1.6.0_11).