Is DMA enabled?
About firmware. It can have a very large impact on write quality. It's best to test out different firmware and determine which works best on your media with your burner.
By Ritek, if you mean RitekG04's (4x capable) then you should usually burn them at 4x. When burning those particular discs there are more errors at 2x then at 4x.
To determine your maximum supported burn speed as well as the disc ID to tell what it really is, download SmartBurn. The link is found in the tools guide in my signature.