TDK support was familiar with this issue, and they diagnosed it as a hardware problem. I sent them the drive and now I'm waiting for my new drive to arrive, so I can test it out.
I think you have the same problem. I'm working with a new pc with w2000 (amd), my other pc was a w98 (intel)with no problem with burning cd's. So I think also that it's a hardware problem.
Today I burned a cd at 40X and it's played in the car, so I hope that the problem is solved. Tomorrow I gonna try again, I let you know.
If You want you may contact me if you have an answer.