I am currently trying to burn an Image to a TY DVD-R 8x disc, Nero writes the whole disc in about 8 minutes @8x, but then fails to write the Leadout completely, i.e. the drive “hangs” infinitely writing the lead-out without finishing it. The only way to interrupt this after even an hour or so is to completely reset the whole system.
I have now had this effect twice, the resulting disc is unreadable then
To exclude burner as cause, can you try with another media and with another software? For example try to burn a media with CD-DVD Speed or with DVD Decrypter (maybe a rewritable, to not waste anymore discs).