I'm hijacking this thread because I had a similar problem this weekend. I would put a blank dvd+r in the superdrive, and a "CDR" icon would appear on the desktop. It was a picture of a cd with the letters "CDR" on it. I don't remember the exact label of the icon, but it was something like "New CD-R." Yet, if I clicked "get info", the size would be correct for the DVD, not a CD. I have an Intel iMac.
Anyway, every time I tried to burn to the DVD+R, I would get the following error immediately: "Burning the disc failed because an unexpected error occurred. (Error code 0x80020000)."
I tried this with several DVD+R's. They were all from the same pack (and were Memorex). Unfortunately, these are the only recordable DVD's that I have, so I couldn't try another brand. (I'm going to the store this afternoon, though).
FWIW, I can view commercial dvd's. A DVD+R (from the same pack) that I have partially filled up on my DVDR (attached to the TV) showed up as a DVD on the iMac, but according to the iMac, a blank DVD. Every blank DVD+R showed up as a CD-R as described above.