Okay, this time I'm not writing with a problem. I had a problem, but through extensive trial and error, I figured out exactly what was causing the problem, so I thought I'd share my story in case it helps anyone else.
I have an external Lacie DVD drive/burner, and use this (via Toast) to copy my homemade DVDs along with my Mac's internal drive.
When copying a homemade DVD, I would sometimes encounter an error message when using Toast, saying something along the lines of "...file VTS-01.-1.VOB could not be accessed (Data fork, -36)." It would also cite an I/O error, suggesting that the disc may have been copyprotected, which it clearly wasn't.
Back in May, I brought this up, and was told to try, among other things, shutting down my Mac for 10 minutes. This worked, but now I can add exactly what *caused* this problem in the equation.
Around the same time (and again last week), I was using iMovie to extract video from a VHS through a Dazzle hookup. However, due to a lack of enough USB ports in the back of my Mac, I removed my external Lacie DVD drive USB plug (which I wasn't using at that part of the equation) and plugged in the Dazzle. After finishing with the Dazzle, I have to replug the Lacie external drive into the Mac. This is where the problem is being created.
Now, I have determined, every time I remove the Lacie external drive to use the Dazzle, I need to shut down the Mac for 10 minutes to before replugging the Lacie drive back in the Mac to copy discs. As a result, the -36 VOB/IO errors have disappeared.
I hope this might help someone if they have a similar set-up.