Plug another source into the same Toslink port you have your Satellite/Cable box hooked into and see if the problem occurs on that source. If it does, it is the 990, if it doesn't it is your satellite/cable box. I have noticed that HD programming is more finicky with my system than the non-HD versions. Sometimes I have problems with the HD program and I switch to the non-HD version on my satellite that problem goes away. I usually notice it when watching the NFL in HD. The issue only last a few seconds then I can switch back to HD.
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Music system
Model 990/7500/Magnepan 1.6 QRs/Technics SL1200 MK2/Aperion S-12 Subwoofer/OWA3/Sony NS75H DVD
APC H15 Power Conditioner

TV System
Large Advent Loudspeakers/ Polk center/Monoprice surrounds/Panasonic Viera 42 inch/Onkyo HT-RC260/Sony BDP S590/Directv


Home Theater System
Onkyo PR-SC886/Outlaw 7125 Klipsch RF-82 L/R,RC-62 center, RB-35 SR/SL, BENQ HT1075, Outlaw LFM1-EX/OPPO BDP-83/Directv
Harmony ONE
Blue Jeans and Monoprice interconnects
APC H15 Power Conditioner