I was not able to burn a DVD or create a disk image with iDVD.
What fixed the problem was my switching from Best Quality to Best
Performance in my iDVD project. Right after I tried this, I was able
to make a disk image, and burn DVDs from that using Disk Utility. (I
wish I was sure of the error number I got before; I think it was
34506. I searched the Apple iDVD forums and found this advice.)
Another thing I did that likely helped was to make more free hard
drive space on my iBook. (That was advice I got at the Sept meeting.)
I had less than 4.7 Gig free, and when I tried to burn a DVD-R disk
from the Finder, my iBook told me I needed at least the size of the
DVD I was burning free on my system hard drive. (I was able to burn
the same information from iPhoto onto a DVD-R. Go figure.) I suspect
that iDVD wants at least 4.5 Gig free hard drive space before it tries
to burn a DVD or a disk image.