DxDiag DDAcceleration & AGP Texture Keeps Disabling

so the title states everything, basically, when i boot the computer or log on, when i dxdiag, on directdraw acceleration and AGP Texture acceleration states its enabled.a couple games from warcraft 3 playing a game called DOTA, when i alt+tab a couple times to, firefox, or music player then back to warcraft 3, it works perfectly for lets say. maybe 3-4 games then when i alt+tab sometimes, and alt+tab back to warcraft 3, it just stays a blank black screen but doesnt crack, just the game does.then i go back to dxdiag, it now states that directdraw acceleration and AGP Texture acceleration is now Not Available.i dont understand, i never had this problem with XP. please someone help or point me to the right direction. ive been at it since 2am this morning and now its almost 11am. been searching everywhere and no luck.