Awkward burn problem :/

I was writing some DVDR’s and all of the sudden they all failed after 70% or so.
I have no idea what this could be, so included the log file that Nero provided.

I scanned for virusses and spyware several times, but the problem persists.

If someone has suggestions, feel free to post.

Drive: Sony DRU500A 1.0d
Media used: Samsung 4x DVD-R and Datasafe DVD-RW)