The 'Basic' theme's scrollbars destroy their outline when the scrollers (both horizontal and vertical) are dragged. The scrollers also appear to shift slightly in their track when moved.
The problem seems to be alleviated by closing and reopening gtk apps. It seems to me that changing themes shouldn't require a restart...
Confirmed
There are a lot of busted themes out there. The only resolution I could really do for this is to remove the theme. GTK+-2.0 allows for more flexibility for themes, so the type of bad-hacks that cause problems like this should no longer be necesary once we switch to that.