Ok guys, I want to know if anyone else has seen this before, and if so, has determined what the cause is. I've submitted a support request, but thought I'd log it here as well. If I get the solution from Autodesk, I'll post it here too, for others.
My Revit UI is jumping when the ribbon refreshes. See http://www.youtube.com/watch?v=f4ujSR0o69w for a demonstration...
My graphics hardware acceleration is OFF, and I'm on Vista Ultimate 32-bit, FYI.