DVD Burning Problem

Hello everyone,
We are feeling severe problem regarding the burning of DVD. We are using Nero to burn a compilation of some wave files to DVD. We make a treee structure like underneath

04072008175055 is Main folder
are its two sub folders

Recordings contains file wave files and Database contains only one database file.

We are using flags ISO_FS and JOLIET
with CLOSE_SESSION and etc. The problem is that the burning process starts perfectly. But on writing tracks it stucks some where in the middle. Sometimes in the starting 25% sometime in the later 25% and some times in the middle.

Even some times it stucks in “writing to cache”
The strange thing that happens is that when we abnormally abort the software and eject the disk. It has free space on the inner side but wrtten some data on the out side. and then it does not read the DVD.
Please give some suggestions about it.