Backup DVD...folders didn't copy

Used Sonic RecordNow to burn a backup copy of my computer documents in my XP computer. As I've done many times before.

But this time I found something strange. The files in many of the folders didn't copy correctly. Taking one folder, for example, I'll see that all of the files/subfolders up to those which start with the letter "C" were, yes, copied. But any file/folder which started with any letter after "C" did not burn.

And the same with many other folders. Up to a certain letter (could be "C", "D", "F", or any letter...each folder seems different) all the files burned correctly. But no files with a name starting with a letter subsequent to whatever that letter is.

Or, with some folders, all the files/subfolders DID copy as they should.

I tried re-burning the DVD a couple times, with a couple different brands of DVD. But the same thing happened.

Anyone ever experience such a thing before?