Recently, when using on the fly to copy DVD's, they only burn at 2.4x, while the media used are Ritek 8x media. When I burn an image, then burn a copy, then 8x works.
I have flashed my Lite-on 167t to disable riplock. My burner is the NEC 2500 (I just ordered a 3500 though) with Herrie's hacked fiormware. Had same issue with stock 1.07 firmware. Seems to only happen with cetrian DVD movies.