MCC003 + A07XL Fw 1.21 Rpc2

I bought a 50 spindle of Verbatim DVD+R 8x printable (for my new Canon Pixma 3000 :stuck_out_tongue: ) but I am having trouble burning them in my A07XLA.

It burned 2 or 3 without problems, but other discs (from top, middle or bottom of the spindle) fail. The burn process does not even start and after a couple of minutes the drive will lock up and crash the computer.

Other discs (eg. SONY08D1) work fine even at 8x speed.

Are the MCC003 newer and not included in the 1.21 firmware? Or did I just get a bad batch? Can I return the spindle (though I already burned some!) ?