After doing an online-update today to the latest kernel 2.6.5-7.108 default, the DVD writer has quit altogether.
Insert the SuSE 9.1 AMD64 DVD disk to make a back-up and K3B signals: "Error, no media found".
CDs still function normally.
Can you still boot from a known good DVD? If not, then I suspect the laser for reading DVDs has packed up.