"In this set up you can only play originally recorded HDDVDs but older formats you'll need to upsample. You'll need to buy an upsampling DVD player which is about $50 worth
Marakanetz"
I hope this was a joke otherwise your ideas and experience is scary. If what you said was true and ITS NOT then analog cable and TV or VHS would not be viewable. If there is some feature I a missing I will say sorry but I have never ever heard of that and I have several both Sony and non Sony HD units that can play any signal.
Also look for "Progressive or 480P" output on DVD or in menu because it may be set to 480I which as others said is for S video and composite. Could also be the DVD player isnt working right or your inputs may need asigned on monitor or even a problem with Tv itself.