Hi Salamander,
Looks like it's a NERO issue to me.
What's the burner you are using?
What's the version of Nero?
Did that Nero version come with your burner?
Can you burn other .iso files to disk
ETC :-)
I did a quick Google for the problem but found no answer, just others having the same issue.
Can you try some other burning software that supports your model of burner?
Cheers
--Steve