I just recently got a Canon Rebel XTi and am having trouble setting the custom WB. In the menu, I scroll down to Custom WB, press "Set" and get the last shot I took (a picture of a white sheet of paper), and I press "Set" again. sometimes it works but a lot of the time, it doesn't seem to take--if I shoot the white paper again, it still looks dirty grey. What am I doing wrong? I don't get the set screen/import image that they show in the manual--well I did once, but don't know how I got to it! Thanks for the help.