I have the same problem The drive won't recognize media like MCC-004 Verbatims, Sony (16x DVD-R, I don't remember the MID) but it works just fine with some really cheap ones (e.g. Raxon) - for this reason I can't just return the drive.
After I burn those discs on my laptop, the 750 will recognize and read them without problems.
Do you think it's "normal" for this drive (i.e. it doesn't like certain discs), or it's defective?
I'm thinking to buy a real Plextor, the PX755 seems nice... but will I feel any improvment?