Audio Troubles while burning DVDs

I recently bought a dvd burner. It came with NeroVision Express as it’s burning software package.
So far the software seems to work well but I am having issues with the audio. If the file is too large to fit on one CD and I have to split it (there is a function for this inside Nero’s movie editer) the audio gets out of whack and the finished product ends up looking like a bad japanese movie with the sound coming a couple seconds late. I have not been able to find any functions to edit audio seperately and it does not show up seperately on the timeline. Does anyone have any ideas on solving this? Also, does anyone know what DVD-9 is???? Nero keeps giving me messages that my media is too large for a standard 4.7 gig dvd but would fit on DVD-9. I have searched the web and can only find 4.7 gig discs.

Any help at all is appreciated!

dvd-9 is a double layer disk only good dvd burners can burn a double layer disk. Mine came with lightscribe tech.