A friend of mine is able to burn Memorex media with his PBDV1640, whereas I can't use them with my DVDR1640P. Any ideas? He has ver.2.5, and I'm using v3.0 firmware.
Probably the firmware difference. Did you try using v2.5 just to check that out?
Yes, I have tried with versions 2.1,2.2, and 2.5. Very strange.