Issue when selecting HDMI for audio

HI,

So I got a new HTPC and I use a DVI to HDMI cable to my AVR.

When playing movies with VLC, I can see DTS displaying in my Onkyo pre pro.

I installed XBMC with windows 8 (Not familiar with win 8... just starting to learn from win 7)

After I installed XBMC... added movies and AEON skin.

When playing movies... Selecting analog as "audio output" it plays fine.. but when selecting HDMI... It does not play well... and audio is fuzzy and video plays in slow motion...

I'm sure there is some setting that I have not done...

Any suggestions, please let me know.

Thanks in advance.