TX-NR616 +Xbox360 sound issues

I have the receiver and the 360 connected via HDMI. This is a new cable; nothing is wrong with it. Sometimes the receiver correctly shows the 360 is inputting Dolby Digital, others PCM. It should NOT be PCM. The 360 is always set to output Dolby Digital 5.1. How can I fix this? It is very annoying to spend the money on this very nice receiver and this be the only thing holding me back from complete enjoyment. Sometimes turning either or both off and on again will fix the problem, but I shouldn't have to do that. Any help or ideas?
Thanks.

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Thank you,

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