Burner not burning DVD's

My NEC 2500a (f/w 1.07) is not burning DVD’s. It burns CD’s fine. I am trying to make a data disc using Nero 6.3.1.10. It goes through the entire burn and everything looks normal. After the burn, the data verification fails and the DVD is still blank. The DVD isn’t ruined. It is just a blank DVD. I have gotten this error with Phillips +RW 2x and Maxell -RW 2x. I have not tried to burn anything on ±R since I started having this problem. DMA is enabled on the drive (it doesn’t work with DMA disabled either), which is the only drive connected to the secondary IDE port.

Any idea what could be causing this?