Hi just loaded W7 MCE and was playing music.  After about ten minutes the system stopped outputing sound out of my two front speakers and instead used the rear speakers?

Anyone else experience this problem? I have a auzentech x-fi prelude sound card and am using it to output analog to my amp.

To recover I go to settings on MCE Sound and setup 5.1 again - start playing music again and its ok - music played from the 2 front speakers.  But after another 10 minutes the music again switched from front to rear speakers mid-way through a song.