According to the evaluation of the bug: 6225472, a non-focusable FS frame will not minimize when ALT+TABing because it is not natively active. But when I push a Non-focusable frame to FS mode and press 'WINDOWS' key or select an application from ALT+TAB menu, the FS frame is getting minimized. When I restore the frame from the taskbar and try the same operations again, it is not getting minimized and behaving as mentioned in 6225472.

I am not quite sure why the FS frame is getting minimized when ALT+TAB in the first time. This is reproducible on WinXP with the following PIT build:
java version "1.6.0-internal"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.6.0-internal-java2d_09_sep_2005_03_26-b00)
Java HotSpot(TM) Client VM (build 1.6.0-ea-b51, mixed mode, sharing)

This is not reproducible on Mustang-b51 because of the bug: 6225472. Hence this is something happening only on the PIT build. I am running it on WinXP-sp2 with Nvidia GeForce4 MX4000 video card.

I have attached a sample test. Execute the sample test. You would see a Frame. Click on 'Show Frame' button. A non-focusable fullscreen frame would appear. Press 'WIN' key (next to CTRL key on the left) or Press ALT+TAB and select an application. You would see that the FS frame is minimized to the taskbar. Restore the frame from the taskbar and repeat the above steps. You would notice that the FS frame do not minimize for the second and sub-sequent trials.