I apologize in advance if this was ever covered in the official Onkyo TX-SR605 forum. I did do a search, but I didn't find anything. The thread is almost 200 pages.
I have a Sony DVD player (older model, but I noticed the same thing with my PS2 and Wii) hooked up through component cables. I then use an HDMI cable to output from the Onkyo to my Samsung LCD TV (4661F). I notice faint, dancing horizontal lines that look like interference. You can see them most clearly on a black screen. This doesn't happen when I use an HDMI cable (tried an Xbox 360), nor does it happen when I hook the DVD player (or PS2 or Wii) directly to the TV. Anyone else notice this? Is it a side effect of the receiver's upscaling/deinterlacing???