Dolby digital plus and Netflix

I have a WD Live Plus and an older Yamaha reciever that can’t decode Dolby Digital Plus.  For some titles on Netflix that are listed as 5.1, I get the regular Dolby Digital signal which my Yamaha does just fine with and I get the 5.1 audio.  But for some titles that are identified as 5.1, I can only get stereo.  From my conversations with the techs at Netlix, I am thinking that this is because some titles on Netflix are encoded in Dolby Digital Plus which is not backwards compatible.  Does anyone know a way the WD Live Plus can be set to downconvert DD+ to DD?  I really don’t want to get a new reciever, and I really want 5.1 and not stereo.  

The reciever is a Yamaha HTR-5490, and it doesn’t matter if I send the optical from the TV (which is getting it from HDMI) or direct from the WD…the problem is the same.

Any suggestions will be appreciated.