I think the problem is with your burner. I use the same Maxell-Hitachi and/or Yuden000 T02. So far, not a single coaster @ 4X, 8X, 12X, and 16X (over 70 DVDs).
Tested software...Nero/Recode, CloneDVD, DVD Decrypter, CopyDVD 3, and DVD2One.
If you still encounter problem with good media and 4X burn speed (DMA ON with at least a 500 MHz CPU), then it's time to retire the old burner. It's difficult to fault quality media when they both exhibit the same problem.
Oh yes, my 4X RicohJpn W11 DVD+RW had at least 30 full burns. No playback issue.