have you recently moved the computer around at all? when i flipped my imac over to put in more ram, the upper right hand corner (not the rest oddly enough) flickered for about a week. the bottom right hand corner is now a little bit lower than my bottom left hand corner, but it's not really noticible. you may have jiggled something in there and it could be your problem. make sure that you have the latest firmware update as well.
i think that the 10.1 cd may have the necessary firmware updates on it. i believe that for the dvse the latest is 4.19 and you'll have to boot into os9 to install it. make sure that you look at the readme to ensure that it's the right update for your model.