Sky HD successfully installed this morning - so far very impressed on LCD HD TV.
I also have the Sky HD box connected to a non-HD plasma, in another room - that plasma is connected directly to the Sky HD box via component video cables, and indirectly using scart cables routed through my DVD recorder/player. I can view the Sky HD box output when connected via the indirect Scart cable route, but when I change to the direct, component video connection, all I get is a sea of coloured lines. Can anybody explain why this might be? Could it just be a poor connection on 1 or more of the cv cables, or is there likely to be some other reason?

I'm not sure if this is relevant, but I cannot even see SD (non-HD) broadcasts via the cv cables.

I'm not sure but I think it might be HDCP related.

what does that mean in real terms?

The Sky HD can output HD over component cables - I havent looked at the Sky HD system yet but you would need to make sure that it is only outputing SD over the component whilst putting HD over HDMI but I dont know if this is possible.

The other option could be HDCP - this is a copyright system to prevent making illegal copies of things but as far as I was aware there is no HDCP on any component.

Just to let you know that the Sky HD box outputs - both SD and HD - are now viewable on the non-HD plasma in 576 & 1080 resolution, via component video cables. I first of all had the red & green cables transposed, and once that was sorted there was a frequent freezing/pixellation problem, which I resolved by switching the Sky HD box off then back on again. All is now fine, and the displays are excellent (almost as good as through my HD LCD screen).