On playback of some DVDs I recorded on my 5005 using my surround sound sytem I discovered I hade no center channel output then discovered no right channel. I tried other DVDs and all was fine. More testing I found DVDs recorded using the front inputs (copy from VCR) were OK only ones using the rear inputs (copy from DVR) had problems. After much trial and error discovered that the right channel audio RCA plug was not tight, and Dolby will not produce a center channel if both R&L stereo is not recorded.
Note: check your cable connections.