There is a long-standing bug in 64-bit XeTeX, which makes it unusable with unicode-math (among other things). It's a serious issue which pops up a lot (e.g., search for "xetex unicode-math 64-bit). The reason was recently identified, see here: http://tug.org/pipermail/xetex/2011-January/019720.html The fix is very simple: http://tug.org/pipermail/xetex/attachments/20110104/61000bdd/attachment.bin (addition of "#include <w2c/c-auto.h>" to texlive-20100722-source/texk/web2c/xetexdir/XeTeX_ext.h). I suggest adding this patch to the ebuild. Waiting for upstream to catch up may take years... I tested on amd64 - the problems are gone.
fixed, thanks
