It may be possible to insert a feeler gauge or better yet crisp flexible plastic in around the three parts of the lens barrel. Maybe that will let you get under whatever gigantic clod of grit is wedging the lens tight. The smallest, inner ring(for the part of the lens that extends out the farthest from the body) is only 8-10mm deep and the next two are deeper. After trying that sort of thing, as well as general beating and assorted ways of turning on multiple buttons etc our SD850IS still wouldn't open. We pulled the outer ring off by slipping a feeler gauge in and around it to release the adhesive. Twisting the next 'cap-ring' (round with the semi rectangular opening in the center) counterclockwise released it and exposed the two lens covering flaps. I took one flap out to have an intact one left to compare too. While I did take them out, what worked was prying the lens out by one of the little bosses, the nub, that held the cap-ring in. It responded to a moderate pull. Maybe the speck I saw on the barrel...