One problem I've been observing intermittently for quite a few versions, without pinning down exactly when it occurs. This affects any library view except 'Panes' view.
What happens is the vertical scrollbar appears to get confused about the height of the main window. For example, here I am showing the last 2 genres in my audio section, but there's a large amount of whitespace below them (and the scrollbar indicates there's plenty more below...)
Other times, it goes the other way; if I scroll to the bottom, there are thumbnails just peeking over the bottom edge of the thumbnails window, sometimes with more below that I can't get to. Sometimes, the scrollbar appears to 'stick', by which I mean it stops scrolling the thumbnails area while I'm dragging the scrollbar up and down.
This can happen any time I move between nodes on the tree, or use the backwards/forwards buttons or hotkeys. If I'm in a particular view scheme drilling down through the levels, it seems to be OK, but as soon as I go back, it's usually (always?) not.
Every time this happens, refreshing the screen (by clicking 'Refresh' or resizing MC for example) corrects the problem.