Not sure which forum is appropriate for this as I don't know whether this is software or hardware related, but here goes.
For years, I've used a Plextor PX-740UF DVD+R/RW DL (actually a BenQ 1640 w/ 164B BEGB F/W) for DVD disc quality testing using DiscSpeed 126.96.36.199. The drive supposedly can use either FireWire or USB 2.0. Because of some older motherboards, whose USB controllers were flaky at best, I've always had the drive hooked up via FireWire and it worked just fine.
Recently, since I've had a newer MOBO with USB 2.0 & 3.0 for some time now, I decided to try the Plextor on USB. Everything looked great on USB 2.0 or 3.0 ports. The drive was recognized in Win7, I could play movie DVD's on the Plextor and run all tests in DiscSpeed with no problem EXCEPT for the Quality Test. The program is able to lock the drive, spin it up and the Start Button comes active, but the Quality Test will never start. It just sits there.
I have a LiteOn iHAS422 external USB drive that will do quality tests with DiscSpeed just fine and I don't suppose I really need the old Plextor/BenQ, but she's like an old friend that I hate to let go of. I just can't figure out why it will do everything I ask when connected on USB, EXCEPT the DiscSpeed Quality Test.