Early shipping versions of the Apple SuperDrive DVD/CD recorder have an issue writing at 2x speed to Mitsui and Maxell DVD-R media. Even though the drive reports it is capable at writing with 2x speeds to these discs, the resulting discs have problems being read in various DVD-ROM drives and
consumer DVD players.
  Answer
The workaround is to manually override the 2x speed in Toast's Write Now dialog and burn at 1x speed. The only DVD-R media guaranteed by Apple to support 2x burn speeds is
Apple's own. See til.info.apple.com which
states that 2x speeds are "Confirmed with Apple media only."
Later shipments of the Apple SuperDrive may not have this issue. All shipping Pioneer DVR-A03 drives with firmware 1.44 or later do not have this issue.