dreaded error #1068 MyClass and MyClass cannot be reconciled

or: why doesn't a switch case without a break work always?

I have got this code snippet as part of a function defined in MyClass

var ni:int, np:int, xv:Number, yv:Number;

for(ni = np = 0 ; ni < cdata.cmds.length ; ni++)
{       switch(cdata.cmds[ni])
        {       case GraphicsPathCommand.MOVE_TO:

           /* A: code here to setup a new path*/

                        var b:MyPath = new MyPath();

                   /* B: duplicate switch case

                        xv = cdata.path[np++];
                        yv = cdata.path[np++];
                        b.add(xv, yv);
                        break;

                   */
                  // fall through
                 case GraphicsPathCommand.LINE_TO:
                         xv = cdata.path[np++];
                         yv = cdata.path[np++];
                         b.add(xv, yv);
                         break;
                 case GraphicsPathCommand.CURVE_TO:
                         xv = cdata.path[np++];
                         yv = cdata.path[np++];
                         b.add(xv, yv, true);
                         xv = cdata.path[np++];
                         yv = cdata.path[np++];
                         b.add(xv, yv);
                         break;

        }

}

the code worked well until I changed the the definition of MyPath and consequently had to change code in the A section.

This produced the - not very enlightening - error message (which suggests to send the error to Adobe but does not give a link)

The script would work again after I enabled the B section