Thanks for posting your message. I am going through the exact same thing with my Onkyo 787 right now....for the life of me I can't the rear surround to work. Using the THX test that comes on the star wars dvd, when it plays the rear sound...the exact same sound is sent to the left and right surround speakers. Not sure how the 787 differs from the 797, but it seems that the 787 doesn't decode the EX format, it will only work if you have a multisource 7.1 or 6.1 input. Really frustrates me, cause I had purchased it thinking it would decode 6.1 EX stuff.
Cheers...Amer
