Hi,
The reason is because ,according to the manual, the computer in only accept progressive input source.So if ur DVD player has this function,select it n will be ok.
Another things to note is not all dvd players does progressive scan on Pal and NTSC software. So if ur software is Pal(irregardless of coding)and u're using a dvd player with only NTSC progressive scan output(refer to manual),there will be no output from the player even if u select the progressive scan mode.So nothing out from the projector too.
So if u only have a component cable n like to use it,just get a component/S-video adapter.Only down side is the S-video dont work with progressive source.Ur choice,good luck!!
regards,