I have Pioneer DVR-810H series 2 Tivo/DVD recorder. It has previously recorded 2 hrs of TV on DVD-R 8x/4.7gb/120 min DVD. A while back, it would burn to same DVD, but only 1 hr content. Now it won't burn to that at all, or to a 16x/4.7gb/120 min DVD. Could someone explain what the problem is, and what I should do to resolve it? Thanks.