Nero has so many burning options so it can be many things, I'll list some potential reasons.
1: Your -rw has more space than your -r and +r?
2: Your -r and +r are not empty?
3: Your burning setup while burning -rw differs from your burning setup while burning -r or +r?
Neros main program can't burn avi files and such so if it is an avi file you're trying to burn you'll have to convert it to an image file or DVD-file before burning or use Nero express, I recomend the first.
It may be easier to help if you write the error message.
I have had a movie on my computer for several months wich I can't burn with Nero. Maybe we have the same problem
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Excuse my english