This occurs with b81 PIT build. It happens on Linux and Solaris platforms.

When a Frame is restored from iconified state, a modal dialog which blocks the frame is not restored. This could be a result of fix for bug 6401700. The testcase could be taken from the same bug.

Run the testcase InvisibleParent.java. Iconify the frame titled 'Frame 1' and click on the 'Show dialog' button in 'Frame 2'. This shows a modal dialog. Now, minimize 'Frame 2'. Now, clicking on the task bar icon of 'Frame 1' restores 'Frame 1' in blocked state. The modal dialog which blocks it is not restored.