I have a SonyDVDrw DRU-510A and it seems to burn fast just half-way, then slows to a crawl, even when recording a standard music CDr.
The CD drive is all alone on the secondary IDE channel motherboard connection.
The DMA is set “if available” (Windows XP) in transfer mode (ultra DMA mode 2).
CPU is an AMD 3000+.
Why does this do this slow-down trick half-way? Has anyone heard of this before. Any suggestions to tweak a setting somewhere?
Hiboo 
This quirk happens no matter what media I use. Mostly I use Verbatim or Memorex CD-r. I can’t tell if DVD burning is slowed down since it is slow anyway!
Last night I timed a burn event (burn speed set down to 16x). Looking at the recording progress bar, at about 30% done it said “3 minutes left” to burn … and then suddenly changed to “17 minutes left” and then proceded to take its sweet time to finish the CD.
This problem occurs with any burning software program I have. :Z