tried with various 720p stuff, latest vlc-1.1.0-rc4 and mplayer from today's svn, stuttering every 3-4 second.
the problem manifests both with gl and vdpau output.
going back to 256.25 fixes things (besides having a 95 degrees cpu temp on the first cpu and 90 on the second
attached are both bug-reports (25 and 29).
I'm here if you need further info.