You've already proven that the projector is at fault here. Apparently, it's a ground loop caused by the projector's electrical circuit not being at the same ground potential as the rest of your equipment.
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Current Setup:
Samsung HL61A750 LED DLP RPTV
Marantz SR5004 AVR / Outlaw 7075 Amp
L/C/R: Ascend Acoustics 340M/C/M
L&R Surrounds: Ascend Acoustics CBM 170
SVS 25-31PC
Panasonic BD55K Blu-Ray Player
Dishnetwork VIP722 HD/PVR.