I have recently (October) moved to a Mountain Lion-based laptop from Snow Leopard. I find that if I have not rebooted within the last week or so, XeLaTeX will just die in the middle of a run. The PDF output is empty. If I give a full reboot to my laptop, it will be just fine for the next week or so. Has anyone else had this problem and if so, is there a fix?
I'm pretty confident this is not a general problem: I very rarely reboot my Mac (running 10.8), and XeTeX works fine. I guess the most obvious suspect would be as commented something to do with the system-dependent font hooks in XeTeX: that is likely to need expertise outside of the TeX area to solve so would be off-topic.