I had a DVD I had created with VisualHub comprising three movies all of which played fine on a standard DVD player. When I went to make a copy of that DVD disk Toast simply kept giving me error problems. I did a bit of googling to see what other disk copying stuff there was for macs and came across a site which talked about using Disk Utility. In desperation I read further and found someone who said if you had an .iso file (which I did when VisualHub did its conversions) then simply open Disk Utility, click on Burn, locate the .iso file and away you go! Man it was that simple and all works great.
Don't know if this is useful to anyone else but I had only used Disk Utility for repairing permissions and the obvious stuff. Now I can't wait to find another .iso file