DMA/PIO was also the first thing that popped into my mind, but recently I helped a friend who had a similar problem. In her case it was the recoding of the movie that took so much time; the total process therefore took 110 minutes. Which actually made sense when I found out she has a Celeron 400 MHz cpu.
Hence the question if it was the burn itself that took forever, or the whole process.
Glad to hear you sorted the problem out.