Where did you get these discs?
I bought a bulk lot of 600 from a reputable importer on e-bay for a total cost of approx. A$ 140.00, marked as SKY silver 'high quality' - probably chinese. I have decided I prefer the cleap Plus disks as they seem more reliable than the cheap minus ones. I mostly use them for Ghosting my machines, 2 or 3 times a week, and if Ghost is happy after verifying them, then so am I - and at that price I dont mind having to do it again if the disk is bad.
Video will work with almost any junk, data is a bit more picky.