ASUS A7N8X DLX Audio Problem

I just completed building a new Win-XP Home system with the ASUS A7N8X DLX
MB, AMD XP 2500+ Barton CPU & 2 512meg strips of Corsair XMS memory. I am
using the on-board audio and latest nForce drivers. Unfortunately, I have
not been able to get the sound to work correctly. I can hear the audio VERY
MUFFLED through my Klipsch 5:1 promedia speaker system. I have tried all
the connections and viewed all of the volume levels but can not get normal
audio. Worse yet, from time to time, it flashes normal audio for less than
a second prior to returning to its muffled state. Any ideas? HELP!!

Thanks,
CM