For what its worth, I am running an audigy zs plat and I just started experiencing this problem tonight. I have played doom 3 in Digital output only mode for weeks with no problems, however i just changed up my speakers and reverted back. There have only been two other changes since yesterday 1.) SP2 and 2.) changed from 9800pro to 6800 ultra. Someone give it a shot with digital only, I doubt the other two reasons are connected.