FWIW - the 64-bit version of OS X is not very stable IMO (sorry Juan) - it will work great for me for a couple of hours and crash on something that I can't always reproduce. I believe that it is a problem with QT on 64 bit platforms as much as it is a problem with PixInsight.
I use the 32 bit version extensively on OS X without issues.
I know this doesn't fix your issue, but I thought I'd share my experience.
Cheers,
Dave