Super-annoying Firefox fail on Mac OS X when any kind of JavaScript alert occurs while print or save dialog is open

A mozilla magazine forum poster, gensym, described it well on March 8th, 2010:

A concrete example is when the "extended running time of a script" is caused by (or triggered while) a File Save dialog is open: the unresponsive script warning dialog will then pop up logically _behind_ the File Save dialog (at least in Mac OS X, panther (10.3) through leopard (10.5)).

The resulting situation is that the File Save dialog _keeps input focus_ (and still has some local functionality), but
both "save" and "cancel" buttons are disabled, so the File Save dialog cannot be removed (closed) and one cannot
get at the unresponsive script warning dialog causing this issue to close that (nor at any other Firefox functionality, not even at "Quit" for a clean shutdown).

The net consequence is that Firefox must be killed and restarted.

The frightening part is this seems to be a long-known bug: https://bugzilla.mozilla.org/show_bug.cgi?id=476541