google "toast error 108" without the quotes. I've found quite a few links that might help you finding out. One message I've found on roxio's boards reads:
"After further reviewing my actions, I realized that this error [number 108 as in your case] only occurred on rips where I had used MacTheRipper to extract the main feature only. On rips where I extracted the entire disc I had no problems. I wonder what file MTR is failing to grab."
Apparently, this really _is_ about video_ts folders missing files. So Toast would be absolutely right to tell you that something's wrong with the video_ts folder. Having several rips with the same problem quite probably means that there's a common denominator in how the rips were made in the first place. What did you use? MTR as suggested in the quoted message above?