I just ran into this problem myself last night when trying to burn DVD-Rs to my new pioneer DVR-212D drive with Vista SP1. I'm having to manually spit the directory that I want to copy into multiple dics, and the first disc burned okay. Both at 16x and 12x, the second one gave me this error:
There was a problem burning this disc.
There was an error burning this disc. The disc might no longer be usable.
I did find this MS post: http://support.microsoft.com/kb/934544.
This describes a possible issue with a '$' symbol being used in the extension of a file name that you are trying to burn in mastered mode.
After searching through my files, I did not find any that used the $ sign in an extension (or file name) of any normal or hidden file.
The files copy fine to Vista from a network share, but something in a certain group of files is rejected when trying to burn to DVD.
I've checked the event viewer, and no other errors are given.
I'm thinking that if it's not a special char that is the issue then perhaps Vista is having trouble with long file names to an extent?
After thinking about this, I'm (and you are) going to have to pony up for some real burning software. Touble is, I've always been dissapointed with whatever I use.