What is going on with my 4570?

I can’t figure this out. Periodically, the drive reads/rips at only 2x. Opening the tray and re-loading the disc won’t help. Sometimes putting different media in or burning a cd instead of a dvd will reset the read/rip rate. Other times, restarting the computer is what is needed. Point is, you never know when it’s going to happen or how long it will last. DMA is enabled and I’ve tried 2 of the available firmware. Any suggestions or tests I can run?

It’s not only the capability of the hardware (drive/system/bus) what counts here, but most and for all the quality of the source (media).

Fire up Nero CD DVD Speed, run a speed (burst) test with the media…

Should I do this even though we are talking mostly store bought DVD’s that are the problem?

Yes.