Tested the following Riteks on my 2500
Ritek TANGO (Overprint) 4X
FWS 4X DVD-R
Datasafe RITEK 4x
Unbranded "Frosted Top" 1x-4x RITEK
All the above disc's will burn on the NEC 2500a and can be read in my Home dvd player but not my xbox except the FWS which will play the xbox.
If I do the same test with my Pioneer 105, all disc's can be read in both Home dvd player and xbox with no problems.
This will suggest that there are different grades in the Dye and the NEC maybe a bit more picky it how it burns them etc.