It says in the specs that it burns DVD+RW at 4x and DVD-RW at 2x so I'm guessing here but it could be the quality of the media at fault here. I know I recently purchased some "eperformance" DVD+R's which were 4x but they would only burn at 2.4x. It turned out that the DVD's were over rated.
[edit]
Just been looking again at the
specs of the PX-708A and the spec sheet is not clear...for instance why would the spec sheet say -
ReWrite
DVD+RW
4X: 5.400KB/s (CLV)
2.4X: 3.240KB/s (CLV)
DVD-RW
2X: 2.700KB/s (CLV)
1X: 1.350KB/s (CLV)
CD-RW
24X: 3.600KB/s (CAV)
10X: 1.600KB/s (CAV)
4X: 600KB/s (CLV)
I guess it's just the speeds it will burn at, but why mention the lower burn speeds?