I'm glad I found this thread.
I have an Onkyo 606, Samsung LN52A750, and Dish Network ViP722.
I have the Dish Network DVR connected to the Onkyo through HDMI, and then HDMI out from the Onkyo to the Samsung. The Onkyo should pass through HDMI signals.
I'm also experiencing random flickers and snow on my Samsung when watching SAT. It's impossible to reproduce at will and sometimes I won't even see it for a week or so.
I also play my Xbox360 a lot but I've never seen this issue with it. Perhaps that's because the 360 is connected to the Onkyo through component and the receiver has to convert it to HDMI out. Perhaps there's only something wrong with the HDMI-passthrough and but not the HDMI-conversion.
I bypassed the Onkyo for a day (went direct from SAT to TV) and never saw this issue, so I really think it's a problem with the Onkyo. I called their tech support and they didn't really know anything about it.
I'm really not sure what to do. Similar to another posted, when the snow is on the TV I can still use the TV menus, and when I change the source and then back to SAT, the problem goes away. I'm thinking of switching HDMI ports on the receiver or maybe using different cables.