i "think" that component CANNOT handle 1080p. i am not 100% certain, but i recently researched that question and i think i concluded that 1080p was not able to pass full 1080p.
i also hooked up an HDMi cable and a component cable from my upconverting DVD player to my HD plasma (it's not a full 1080p plasma, but does do 1080i and 720p).
on my DVD player, i chose to send out a 720p signal first and then a 1080i signal.
i ran both of those resolutions into my TV via HDMi and then component.
with the signals into the TV, i had the TV tell me what it is displaying. for the component signal coming out of the DVD player at both 720P and 1080i, the TV was only able to show 420p using component cables. using the HDMI, i was able to get the 720p and 1080i to display on the TV.
so, assuming i did my test correctly, my assumption is that component cables cannot do anything more than 420p.