So I get an HD-A1 HD-DVD player and a Mitsubishi HD1000 projector. I'd like to compare the image between the HD-DVD version of a movie and the DVD version on my old Zenith DVB-318.

As soon as I switch from the HDMI connection to component on my projector, the HD-A1 goes to stop because there's no valid HDMI connection. This sucks.

Thanks, Hollywood!

That's as much your projectors fault as the players. My TV doesn't drop the HDMI link when I've switched to another input as long as I don't turn the set off. My A1 stays playing just fine when I flip over to check a TiVo recording or something. That said, the whole "must have HDCP to play" thing is a drag, exspecially when they'll let you watch over component in any case.

As the previous poster said, this is not necessarily due to HDMI. Some displays will not shut down the unselected HDMI inputs and will keep the content protection going even when it's not selected. There's no requirement from the HDMI or HDCP side that says you have to do it one way or the other- it's a decision the manufacturers to choose in their design.

the whole "must have HDCP to play" thing is a drag, exspecially when they'll let you watch over component in any case.
Yes, they do, but this way they can control quality: with Image Constraint Token flag set, component output will be reduced to 960x540.