K3B problems

There is a reasonably long thread on MepisLovers about this (regulars).
I upgraded to 6.5.02 (64 bit smp) and could no longer burn data CDs.
The hardware is a Pentium D 945 3.4Ghz duo with a Pioneer combo optical
drive model DVR-112D. I now have a large collection of drink coasters.
The errors occur after burning about 10MB and I got "write failure" or
occasionally "could not fixate disk". I could burn audio CD successfully.
I downgraded to 6.5(32) and my first attempt to burn a data CD was 100%
successful. So three things changed: 6.5 to 6.5.02, 32bit to 64bit, and
single cpu to smp. Obviously I'd to take advantage of my cpus - so what
do I do next?