What happens is that Nero Linux which has been opened by say UserA does not have read/write priorities on the burner.
This means that you don't have access to the burner. You will notice that if you run nerolinux as a root user, you will see the DVD burner listed.

What should you do in this case? My workaround will solve this issue:

Step1:
Know your dvd burner's drive name. It should be something like sg0 or cdrom or sr0. To be sure, type:
su
mount
In the list, search your dvdrom (put a cd before and let your linux automount it so that the drive name appears in the list)

Step2:
Get the path. It will be something like /dev/sg0 or /dev/cdrom etc..

Step3:
Set the required permissions on the drive.
chmod 777 /dev/sg0

Step4:
Happy burning!

Hope that helps!

Shailen Sobhee
Mauritius