Using Win 7 Professional, 64 bit.
I got the 8 MB remover so that i could test my map on LAN and tab out while the game plays out... Now I don't have to do that, pretty handy actually ^^
Not sure if it matters at all, but to clarify, I tap windows key. I'm not actually alt+tabbing out of war3.
edit: This bug doesn't seem to happen everytime I'm minimizing war3, which is odd.