Well the bug is that when a contact has colours with their name, and it goes more than the contact list width, the colour goes over onto the scroll bar...
here is a picture of it:
also:
Windows XP Service Pack 2 (5.1.2600)
Windows Live Messenger 8.5.0517
Messenger Plus! Live 4.22.0.274
Enhancer (Script)
EDIT: this only happens every so often...
EDIT 2: i just changed the width of my contact list by 1 pixel, and let it retreat with enhancer (docking to top) then looked and it had the bug again