Paint Peeling off new Plaster

[nicksey]

Any ideas on what causes paint to peel off new plaster. This is a room that was replastered some weeks ago. it is now completely dry and has been painted with a reasonable quality emulsion paint. It is OK almost everywhere but there are about 4 small patches where the paint just won't stick to the wall. When its rollered on it just peels off with the next sweep of the roller. If I brush it on it stays but bubbles up and cracks as it dries. Any ideas on what's happening?