I'm sorry, I don't know anything about JAWS...  Theoretically, if it would ignore JavaScript then pages should be OK, given the fact that the menu is defined by plain HTML lists.  If it crashes though, it means that it either tries to execute JavaScript code or tries to use the full existing DOM (after having been modified by DynarchMenu), both of which can be bad.

An easy workaround would be to identify a JAWS browser in your server-side scripts and if that's the case, avoid the DynarchMenu.setup line.