Bluray 1080p Question/Problem

[Rockblaster13]

Hi all,

I have upgraded my pc recently so that I can watch Bluray on my pc.

I have the newest and also update for WinDVD9 Plus Bluray software installed.
The newest version of Arcsoft Total Media Theatre.

Now my question/problem is when I insert a Bluray disc and play it, the quality is amazing. It uses a 1920x1080 (Full 1080p) resolution at the menu and all but as soon as I click play to watch the movie itself the quality goes down. It wont fully use the 1920x1080 resolution anymore.
I tried playing "The Golden Compass" , Transformers and some more and they all seem to do this. The Golden Compass which I have right in front of me says that it will play at 1080p so what gives?

Oh almost forgot to mention that the Behind the scenes ( Disc 2 of transformers and The Golden Compass) also will run in full 1920x1080.

I have tried using a different DVI Cable, different bluray players and got the same results.

Does anyone know how to fix this problem?

My PC Specs:

BenQ FP241VW (24" LCD with a 1920x1200 Resolution) I am using the DVI connection.
EVGA GTX260
LG Bluray Drive
Creative X-Fi

Let me know what more info. you need.

Thanks in advance for your help.