DVD burner can burn OK but won't read disk?

[impmon2]

I have a Lite-On burner 1693 and it burns CD and DVD fine but if I read any disc, it can't read any and reports an empty CD or DVD instead.

Burned CD and DVD plays fine on other drives and on DVD player so I know it's burning fine. So any idea why it won't read a known good disc (including its own burned discs)? Does the burner use separate laser for burning and reading?