Copying standalone discs to pc problems



I have 2 dvd rewriters and am having the same problem with each. I copy from tape to +RW/+R and finalise the discs. They play fine on my PC and other standalone players. The problem is I can’t make copies on my PC from them. DvdFab seems to rip the files ok but DvdShrink doesn’t recognise them, ‘invalid data in file’. Nero analyses only about 40% then crashes. Anybody any ideas? My burner is an Ibox.