I had an interesting experience with shelling, that I thought I'd share and see if anyone could enlighten me. I'm working on creating what will be a thermoformed clamshell. Yesterday I was working on the attached piece, I selected several edges and applied a fillet, and immediately thought that I'd better see if it could be shelled, I had a concern because of the relatively complicated surfaces . I applied the shell with an amount of .015", and it shelled without any problems what so ever, which surprised me a little. I opened the file this morning to continue work on it and it wasn't shelled, I assumed that I had forgotten to save the file after I had shelled it. I selected the back surface to shell it again, and this time it won't do it. I'm a little stumped by it working fine yesterday but not today. Any thoughts or reasons on this?

Thank-you,