Run the attached test. It shows two frames and a window with a button. One of the frames (the right one) is a parent for the window. Press the button, so the window gets focused, and then press the title of the left frame. If you see JVM has crashed, the bug is reproduced.
The bug can only be reproduced with 7.0-b02 or later. I suspect this is the fix for 6359035 that has some impact on this problem. That fix contained the code which changes the way how AWT native components are subclassed.