I am having the same problem. (chord window will not scroll, but top of window gets over-written in a messy way) It seems to only happen on long songs (otherwise why would it need to scroll).

FWIW I have 1920x1200 screen resolution, which I think might have something to do with it, and I have three of those monitors on my system (which I don't think has anything to do with it).

Unlike some of the other posts, this happens to me very consistently, and rebooting or whatever does NOT help.