Tried to paint "popcorn" ceiling in upstairs bedroom. "Popcorn came off in spots instead of paint going on! We tried oil based paint. Within a week it began to crack and peel in spots. It seems that the drywall must have been contaminated by something, because when we tried to scrape the stuff off and it will only come off certain spots. What a mess. Need help!. We are hoping that we do not have to replace the drywall. Some spots on the wall of the same room are behaving the same way. New paint cracks and peels no matter what we do.