Sony DRU 510A DVD±RW Burner "disc supports speed compatible drive" Questions

compatible DVD-RW media only. Why won't it recognize 4x blank disc's anymore? Well a quick check here says it should manage 4 x DVD write speeds:- http://reviews.cnet.com/dvd-drives/sony-dru-510a/4507

...supports cables as long as 90cm without sacrificing data integrity and system reliability. Hence Athena SATA controller can be installed on the top drive bay even in an 11-target tower duplicator. ...

...Disc Size: 120 mm, Maximum Transfer Rate: (F h) Number of Layers: 1, Track Path: Parallel Track Path (PTP), Layer Type: recordable Linear Density: 0,267 um/bit, Track Density: 0,74 um/track Starting ...