1) Go to this spot in the IVP New Testament Commentary on Romans
2) Start dragging a selection from the first paragraph beginning on that page ("The Believer and the Law...") on down until you scroll to the next screenworth of text and the top of your selection has scrolled off the top of the screen.
3) Release the mouse button.
4) Hit PageUp.
Result: you get a weird overlapping selection:
Note there was no highlighting in that resource, so this is a repaint problem with the selection overlapping a scrolled version of itself.
I can reproduce this at will in other locations, so that particular location and place to start the selection probably doesn't matter. Basically just drag-scroll a selection until the top of it scrolls of the top of the window, and then let go and page up. But in case you had trouble reproducing it I wanted to give an exact scenario.
