oh, btw I recommend decreasing your image size. 3m (I'm assuming horizontal) is too much for the NEC VT-47. Also, with a native resolution of 800x600, 1080i is overkill. Stick to 480p or 720p for better results.
Also, since you're so certain your cables and connections are not the source of the problem, there is obviously only one answer: poor AV pack quality. In any case, I would try using alternate cables, if possible, just to make sure.
If possible try using the same layout with a component-out capable DVD player and compare the images.
edit: typos (need sleep)