I am running the beta bios and I've found them to be the fix me for so far.. I'm running turbo mode in the agp driver, optimal in the bios also. I've had the same problems everyone else has with all other bios including 1003.. it helped the situation but did not fix it for me. I don't know if your video card chipset matters, I'm running a GeforceMX right now.. I ordered a All In Wonder Radeon, not only because it owns but because my cousin has a Radeon 32mb ddr and is running the exact same setup I am but with bios ver 1004c in optimal mode and turbo agp. He has no problems that my computer has shown.
Yet I *seem* to have it fixed now with 1005. I havent gave it the complete test such as DVD, Q3A time loop demos but the random windows freezes are gone.
A quick way for me to test a certain setup for lockups in the situation that we are all in I do this first.. if you have a mouse wheel button click it in a email message you have that is long and requires scrolling.. click the button so it stays as if you were just going to move the mouse down and let the screen move down but move the mouse up and down really fast.. you'll find on a very unstable setup it will freeze within 2 seconds or more.. sometimes it takes a while longer for this to occur in different bios versions and settings. That is my very shallow, yet useful first test for our mutual problem.
Next I try just letting a DVD run all the way through, as a unstable setup won't be able to handle it.. or Q3A on a demo loop.
Hope my experiences help someone else! And don't forget to try switching to Radeon.. even Asus' own Geforce cards are suggested only for intel chipsets!!