Severe banding when playing Hi10p mkv

I get severe color banding when playing 10-bit videos. It appears as if VLC is rendering video with 2-bit color (i.e. 64 colors). Otherwise, video and audio play back smoothly, occasionally stuttering in scenes with rapid changes. CPU usage is around 25%, but may reach 60% momentarily. This banding problem occurred in version 2.0 and continues in today's 2.1 (64-bit) nightly build. Interestingly, if I take a snapshot within VLC, color is rendered correctly, but the Mac OS screen grab attached does show the problem. Other media players using FFmpeg (e.g. Movist 1.1.5 and MPlayer2 rev14,) seem to render Hi10p just fine. My MacBook 2,1 runs OS-X 10.6.8 and has a 2.0GHz Core 2 Duo with 4GB RAM installed, 750GB Momentus XT and Intel GMA 950 video (bleh!).