Hi Nick25, "component interlace and component progressive" settings only relate to the component outputs and have no effect on the DVI output. So, if you are just using DVI and Scart, leave the setting on Scart.
Incidentally with the Denon 1910, when cycling through the DVI modes with the button on the front OFF>480p/576p>720p>1080 - note that RGB is disabled on the Scart output (and it becomes composite) except when DVI is OFF (and the little orange LCD on the front of the player goes off). So if watching through Scart make sure DVI is off (you will probably watch most DVD movies via the DVI output, but may prefer some DVDs - those shot on video perhaps - through Scart).