When we had our 1922 house's interior painted in 2006, the painter told me that it was going to be a problem to paint the living room ceiling. He showed me a small section that he'd painted. The surface was beginning to sag. He said that it was common to cover ceilings with a taut sheet of canvas adhered to the plaster above to make a perfectly smooth surface. (Sometimes they were decoratively painted.) The canvas on our ceiling is beginning to pull away from the plaster, not only where the painter discovered the problem, but in other places. I thought they were just weird cracks, but no, the canvas is coming off. The painter said that the wetness and weight of the paint were going to cause problems, and advised us to forget painting this particular ceiling. Could something similar be happening to you?

thanks vjrnts - we don't have canvas on our plaster, although sounds interesting...... we like most ppl have had extreme cold for the winter and the heat has been running constantly, no surprise there. So part of me wants to think that it's related to this. We have huge cracks between the crown and the ceiling in our master bath but that was an addition and it usually closes back up. Should prob. say that all the interior was professionally painted and primed first with porter paint. The guys were here for about 2 months painting.

Do you know for an absolute fact that there is no "canvas" or other material there? I have seen hundreds of homes where is was pretty much un detectable.

Install 1/4" drywall over the whole thing; prime, paint, and forget about it. Looks like you could butt to the crown mold with no problem and use latex caulk between the drywall and crown.