Hard to say what is going on there. I've only used Audyssey in a smaller room (11x17x8) and always with an Onkyo.

Have you posted this in the Audyssey thread on AVS? Chris (one of the Audyssey founders) helps folks with their setups.

http://www.avsforum.com/avs-vb/showthread.php?t=795421

Dave
Audyssey Setup Guide