Joann, I have had a very similar problem - wallpaper on drywall. My walls were painted previously, and that was part of the problem. They had not been sized properly on initail paint so the paint (a silk vinyl) became brittle. Thus even the paint had to be removed before we could put anything else on. I ended up using a very small grinder on a very slow speed with 60 grit paper and this did the trick, but I ended up having the drywall skim coated with plaster in the end to get the finish I wanted. Nevertheless it was worth it, because it was cheaper than ripping out the drywall and starting again!