Using Windows 2000, I get similar results to those of KS. The "Tree:" section works perfectly, but the "List:" section does not. Sometimes the window/box containing the list will disappear (or change size) along with the scroll bars until I let them go.
The difference appears to be how fast I pull the scroll bar down, and whether or not I pull it off the program window (past the border of the SkinTree window). If I stop before crossing that border, only the scrollbars disappear. If I continue past, the bars and list box disappear.
When using the horizontal scroll bar, the whole box never disappears. Unlike the vertical scroll where everything disappears, the box just gets smaller (horizontally). The scroll bars still disappear though. In this case, it doesn't seem to matter whether I stay within the border or not. Rather, it seems to be more related to how fast I move the scroll across (the faster I move it, the smaller the resulting box).