I reported this bug before, and Andreas developed a patch to fix it.
However, the patch has apparently fallen through the cracks, and the
bug is still present in 1.4.0pre2.
The problem is this: LyX-140 on Mac will crash *when using key
bindings* for File > Open, File > New, and File > New from Template.
It will not crash when using the mouse to select these from the
menus, nor will it crash dragging and dropping files into the LyX
window.
The successful patch can be found here: <http://www.mail-archive.com/
lyx-devel@lists.lyx.org/msg81627.html>.
Bennett