16:9 content squished in 4:3 area on widescreen TV

When I burn a DVD that's made in Encore using the 16:9 mode it plays in 16:9
mode on my computer so I know it is burned properly. I go to place it in my
Xbox360 and 2 other DVD players it does no auto expand to fill my 16:9 TV. (it
is squished in a 4:3 image) If I put in a commerical DVD such as a movie from
Blockbuster/Netflicks both my XBOX360 and the 2 other dvd players auto expand to
fill the 16:9 video over the entire screen automatically with out me chaging the
screen settings on my tv.

So why does this happen with my home made DVD's that are set to 16:9 and play
fine on my computer? I know my players are set up correctly because the
commerical dvd's work properly.

I've used IFOedit and checked my flags of the DVD and they are set correctly as
the dvd does play fine on my computer. So any idea why my xbox360 and 2 other
DVD players have issues playing my DVD and auto expanding it to widescreen.

I've even tried just burning 16:9 a menu to a disc and the same things happens.
What needs to be done to make these DVD's auto fill my widescreen TV like
professional ones?

Encore squashes them?
In preview, or on the final disc?
If the former, is PAR correction being applied in the preview window?