Dolby Surround Missing Right Surround Track on Blu-ray

I author a large number of DVDs in Scenarist for our standard def applications,
but recently, tried authoring a strait through Blu-ray disc with Dolby Surround
5/0 audio tracks with some peculiar results.

I've encoded the Dolby track the usual way, with Scenarist's Dolby encoder, and
imported it along with the m2v video track in to Encore and burned a Blu-ray
disc.

The front channels play normally, but the surround is half missing, or perhaps
3/4 missing, when accounting for the fact that the left surround is about -10dB
from where it should be, and there is NO output at all from right surround.

At first, I thought it was because we encoded at 640kbp/s, but I am told this is
a legal bitrate for Blu-ray Dolby surround.

So that leaves Encore as the remaining suspect.

SD DVDs encoded in Scenarist with this Dolby encoding method play as they
should. The difference here is we're using HD video and encoding to a Blu-ray
disc.

Might Encore be doing something to our Dolby tracks? Is it confused because the
LFE channel is missing? Or is Encore unable to handle 640kbp/s Dolby surround?

Hmmm, then I'm puzzled by this... if I encode AC3 and use it on a standard def
DVD, it plays with all surround channels. If I use the AC3 file in an Encore
project to make a Blu-ray disc, the left surround is barely audible and the
right surround is silent.

It's either got to be my Sony BDP-S301 can't handle 640K audio, or there's a
possible bug in Scenarist's Dolby encoder when using bitrates higher than 448K.

This is taking a while. 7 hours to burn 17.5GB? Disc has been writing for close
to 90 minutes with 6GB written so far.

Mark.

640kbps is perfectly stream-legal for Blu Ray Dolby Digital.
What I am wondering is about the validity of a 5.0 soundtrack though?
Could be wrong.....
Another distinct possibility is the encoder is somehow not outputting BD-R legal
streams, but this is unlikely - although AFAIK if you are using Scenarist 3.x or
earlier, then it possibly isn't Blu Ray qualified? Again, as the encoder is
fully Dolby Labs certified I sort of doubt this is the problem.