480p is a normal tvs display, a plasma tv uses 1080i, an hd display, you're attemting to display a 480p signal on a 1080i display, making the signal weaker cause its only using half the lines, hence the HD A/V pack, which upconverts the 480p signal to 1080i, progressive scan is hd, only hd tvs have the ability to use progressive scan, ive done vast amounts of research on tvs, sinve i want to work in that field, if the signal that is being sent to an hd tv, is not an hd signal, there will be delays, buy the hd a/v kit and your problem will go way
also halo is 1080i, i have an xbox magazine that explains it further and halo is the game used to show the difference