===== What happens if a faulty overlay causes a break in the simulation run? =====
In a packaged image, the cause of the break is displayed in the instrument browser, in the same manner as a non-overlay break.  In an open image, the debug window will show the faulty method which will contain only a comment that an overlay exists ("Cannot access source code for #//METHODNAME.//"), rather than the code itself%%--%%which admittedly makes debugging more difficult than for non-overlayed methods.