When you say "left rear surround" do you mean "left side surround"? I ask because the Model 950 has a 5.1 analog input, meaning the multichannel analog input doesn't support the rear surround channels - just fronts, center, sub, and side surrounds - and there are very few discs that actually offer 6.1 or 7.1 tracks. If you connected the rear surround outputs from the player to the (side) surround inputs, you may not get much content.
If you do mean side surrounds, I'd suggest connecting a known and trusted input (center or a front channel) to each of the 5.1 analog input's connections and determine if they are all working. Be sure to use a disc that you know is providing content for that channel. A calibration disc like Digital Video Essentials would have channel test tones that could work for this, or you could use a left or right output and a CD.