Re: GT230M and 195.36.24: Stuttering when playing video with HDMI
The XBMC results are odd. Perhaps the audio clock is simply incorrectly configured, so it's spitting out the audio too fast, and XBMC is trying to keep the video in sync with audio.
Can you try an audio-only application (play back an MP3 or CD rip or something) over HDMI audio. Is that also way too fast? I assume the fast audio is also very high-pitched?
Are you using any special kernel or audio drivers for the HDMI audio? I vaguely recall HDMI audio being supported on that card only very recently. Perhaps you need an updated driver for that.