Your blanks use a dye/ink that's rated for up to 16x burning, and your burner says it only supports burning them at 4x, which shows it has poor or not support for those blanks. Not to mention that we know from our experience that CMC MAG dye blanks are rubbish.
That being said, Verbatim and Taiyo Yuden are the best blanks you can buy, and if a burner doesn't work with them then you can be sure the burner is faulty.
By the way you should install service pack 3 for your Windows
//edit: too slow again