@Cheetah: I will try it, but I feel this is not my problem. My problem is - just a feeling - ArmA try do something (maybe connect to the internet) in every minutes. My hardware can run ArmA, the 3D engine smoothly. But when I in the editor (a 2D map, no need processor or 3D accelerating), all Windows halted for 3-4 sec in every minutes. I can't move the cursor in the ArmA editor, or I can't type in a Notepad... etc.
Yesterday I patch up my ArmA to 1.05 and I saw the problem will be better twice. Now "only" in every two minutes halted for 3-4 sec.
@Jester: P4 2.4, 1Gb RAM, Gef6600GT 128Mb