White screen after sleep using 10.8.3

Ever since I upgraded to 10.8.3 using the Combo update, whenever my computer wakes from sleep, I get an all-white screen. I can "select" parts of the screen using the mouse and the regular wallpaper comes into view. At that point I can use the computer just fine. I have re-installed the combo updtae and restarted the computer but the "white-outs" keep happeneing. Any thoughts as to why this is happening and what I can do to fix it? Thanks.