Could be many things, or combo of such, like XP or Vista, graphics card w/ under 250MB, less than high speed cable, and low wireless signal, or any combination. I see this sometimes on my Dell 410 running Win XP pro, Nvidia 7400, and wireless-G. My Toshiba M-64 w/ Win 7 Premium and wireless-n has never done it, tho. May be time for some new gear.