I have the same problem. Only happens occasionally when I accidentally hit a wrong button on the remote. I can't seem to recreate the problem on purpose so I'm not exactly sure why it happens. It can be fixed by unplugging the 990 or turning the main power on the rear off for 10 seconds or so, then firing it back up. I reported it to outlaw and per their recommendation loaded the latest firmware, but it still happens occasionally. I just live with it. See the post below entitled "PLZ Help DD has distorted sound".