Windows 7: Screen stays Black For Long Time after Alt-Tab

I am Running Windows 7 64 bit, I play a game called Warcraft 3 The Frozen Throne, and when I alt Tab out of the game and then back too the game my screen stays black for like 30 seconds before going back to the game, its been doing it since i bought this new Acer monitor I am running

Windows 7 home premium 64 bit
AMD Phenon II 1035t x6
ATI Radion HD 5400
acer p215h 21.5wide

It doesn't do it all the time tho, sometimes it will stay black for 1 second 5 seconds 10 seconds 30 seconds and sometimes black for like 60 seconds.

How much RAM do you have? And what resolution do you play on your monitor? Do you have it at the highest resolution it supports?

i have 4gig ram, yeah its at hishest resalution, 1920x1080 orientation is landscape.

some games doesnt allow to alt+tap
just saying

its always worked before, just doesn't work now with this new monitor, well it does work the screen just stays black for a very long time before going back too the game.

Try playing it in windowed mode at the highest resolution. On the shortcut, add -window to the end of the "Target" field. If you keep the resolution at the highest setting then it should still fill your monitor.