Re: Dialog from center speaker
Check your DVD menu and be sure the language is set to: English Dolby 5.1
Some DVDs don't have this option or, even if you do set it for "5.1" it may only have 2 channel sound. Check the DVD case and see if it specifically says "5.1".
If it is not a 5.1 DVD, see if you can set your receiver to "Dolby Pro-Logic" That usually takes care of my VCR sound problems.
And, paraphrasing what is said above, if it does it on all DVDs, there may be a problem with your receiver.