Getting message, "Maybe this disc is blank or open-sess

[ZoneIII]

I haven't received an answer from Ulead for the question I posted earlier about not being able to navigate to my files/images for DVD burning so, in the meantime, I installed a DVD-R drive that I had on hand in place of a CD R/W. (I guess I should have had it in that configuration anyway.)

So, now I have a DVD reader and a DVD burner and I should be able to do a direct DVD copy. However, I get a message when I try to do that that says, "Maybe this is a blank or open-session disc. If it is an open session disc, please close."

I don't know why a blank disc should work (assuming it is talking about the disc I am writing to, and I don't know what an open-session disc is,let alone how to close it. I tried rebooting my PC but I get the same message. I ran across something about open-session discs earlier when trying to solve my earlier problem but I can't find it now.

What does the error message that I am getting mean and how do I fix it?

Thanks.