TOSHIBA SD-R5002 and Primos and Nero

Hello folks,

I bought this toshiba dvd burner and some problems with PRIMEON 120Min./4.7GB DVD-Rs when i convert a movie with dvd2one and want to burn with Nero. The DVD writes but when writing lead out a error message apears writing to disc not succesfull but i can watch this disc on my hardware dvd player .
whats going on ? is a burner or a media problem ?I hope somebody can help .THX