DVD Burning completes ok, but disc blank (Nero 7)

Hi, I have an issue with Nero 7 burning DVD’s.
I’m first using Nero vision to create the video files and then using the DVD Video option in Nero to create a DVD disc.
Also it appears to be intermitttent.
Burning completes ok but I’m unable to play the disc, windows reports an error that the disc is not compatable.
However if I go to check the disc info through Nero, it tells me that there is 3.5GB of data on the disc and it is a data mode 1.
any help is much appreciated. . . thanks