After some playing around, it did turn out to be the DVD player I was using. Pulled a DVD out of my collection, and it had the same cutoff, left and right.
Canon HV20 shot in HDV mode -> Premiere CS4 HDV 1080(60i) -> Dynamic Link to AE CS4 HDTV 1080p comp, render lossless -> Premiere CS4 export rendered file as MPEG2-DVD, quality 5, 29.97 drop-frame, progressive, widescreen, VBR 2 pass, min-6, target-7, max-8, no multiplex (get two files instead of one), PCM audio, clicked the filter box and gave a value of 1 on Gaussian blur, which softens the image.
I put it onto a DVD and it looks great on my Tube TV with a DVD player, and on my HDTV with a Blu-ray player.
I hope this helps somebody else.