I have my X-box360 connected via Components on my Panny, and so far no sparkles of any sort. You can try this:
1)Locate the spot where you saw them sparkles
2)Switch off the 360 and close your lights (keep the plasma on), look at the same spot again. If you can see brightly lit dots in the same area, then you have "stuck" pixels.
By the way, my 360 is a first generation model, so it does not have those HDMI ports.