This bug is a tad difficult to explain, so I will first define it and then give you an example.
In ZQuest, if you click and hold on any part of the window that isn't the editable screen, the combo sidebar, or the menu at the top of the window, and move your mouse around, the cursor displays improperly--it's really jittery and slow. For an example, click and hold the combo drawing mode button and move the cursor around. This happens in a bunch of other places, too, like the panel below the screen being edited and the frame of the favorites panel.
Now, I understand this is a very minor bug and it doesn't significantly affect how the program operates so I don't totally mind whether or not the effort is put in to fix this. But being unintended behavior, I figured I'd report it anyway. 😉
I use Vista and run ZQuest in large mode, full-screen.