PIT : Internal frame menu goes behind AWT Canvas in 6u12 b02 pit build

I have a JFrame which contains desktopPane. The DesktopPane contains two internal frame, which intern contains AWT Canvas. When i invoke the menu of the intenal frame.The menus goes behind the canvas, this works fine in 6u12 b01 promoted build, but fails from 6u12 b02 pit build. Hence its a regression. I have attached the screen shot of both 6u12 b01 promoted build & 6u12 b02 pit build.

Step to reproduced:-
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1) Run the attached testcase either in nimbus or windows look and feel
-Dswing.defaultlaf=com.sun.java.swing.plaf.windows.WindowsLookAndFeel for windows laf
 -Dswing.defaultlaf=com.sun.java.swing.plaf.nimbus.NimbusLookAndFeel for nimbus laf
2) Move the red internal frame away from the yellow internal frame.
3) Click on the internal frame's java icon. Observe that menus goes behind the canvas, if you see the same then the bug is reproduced.

I tested this on windows xp sp3 with 6u12 b02 pit build.