I have the same trouble than you (device buffer empty when the program's buffer still full...), excepted that it happen only a few time when burning (2-5 times) But when I see your ibg files, I understand that there is nothing to compare...
I have a nec 2500a, asus a8n-sli (nf4), winxp 32bit, media are phillips 16x dvd+r and 60% humidity in my piece
If I find some fix, I'll post it here. Good luck.