I'm a new SW user, with extensive experience in AutoCad (versions up to Inventor '08).  Using SW Pro '12, Win7-64, I was working on a valve body with several threaded bosses, threaded holes, etc.  I had this body in an assembly where all the attached parts were nicely constrained, and beautifully displayed via a section view.  I was doing modifications to the body to thread several of the holes the hard way, i.e. draw a triangular cutting profile, then sweep cut using either: a helix path, or a straight line path with the "Twist along path" method.  I had this thing looking good, with threaded features following the threads via the Mechanical Mate, Screw function.  Boisterously showing off to my boss what I had accomplished on my first SW project.

After completing my very last threaded hole (a 1/8" pipe taper hole) on this part, I discovered that my part would no longer perform a proper section view, with an error:

"The model could not be properly sectioned by the section line.  Please check that the section line cuts through the model."

Also, one outer surface of the solid part is gone, and the part is shelled out.  Al the threads, features, surfaces within the part are visible from within the part as though there is no solid body, just very thin surfaces.  Now my Assembly is ruined because of that particular issue.  I saved the body under a different name, then deleted many of the features of this "new" part, starting with the newest, thinking that I'd done something stupid within the creation of some feature, and backing up would eventually fix it.  No dice.  I reverted the part back to well prior to the shell problem, in fact deleted ALL of the threaded features, and can again do a section view, but the part is still "shelled".  I'm stuck.  Did I, in my furious experimentation, set some parameter that hosed me up?  I would have thought that reverting to or rolling back (using the hand tool...)

I can post files if anyone thinks that would help.

Thanks in  advance for any help.

Ed