Help XBMC Frodo and HDMI audio output

Hi guys, I recently bought this alienware x51 computer for my living room. I noticed that if I use XBMC and select HDMI output from audio settings everything works great. But then if I leave and come back (turn the tv off for a while), the audio doesn't work and I have to go back to settings and select HDMI output again in the systems settings (XBMC). Anyone have any suggestions?
Kind of annoying
Thanks!