I was able to download the tarball, build it in /opt and run LyX 2.0.3 successfully. Clearly this is a Gentoo packaging issue of some kind. I then went back and tried some other things and now LyX runs correctly! I performed the following steps, which may not make much sense to you unless you're a Gentoo user:
* Re-emerged lyx (tried this yesterday). Still crashed. * Updated world * Re-emerged qt-core and qt-gui. Still crashed. * Logged out and logged back in * Messed with xetex and luatex USE flags. Previously, hadapp-office/lyx xetex -luatex in package.use. Removed xetex flag. * Re-emerged lyx. Now it runs! *Re-enabled xetex USE flag and re-compiled LyX, although I had to put the xetex flag in make.conf in order for LyX to recognize it. LyX still runs! Now, does it run because I had to re-emerge qt and then re-emerge lyx? Did I need to log out to unload the old copies of QT from memory? I thought I had isolated the xetex flag as the problem, but now that works fine too! Thank you to everyone who invested time in this...I wish we had a better resolution than "tried random stuff and it worked." My best guess is that it has something to do with the exact order in which I installed TexLive, LyX, and QT, and the USE flags that were enabled at the time each was installed. Portage is normally really good about finding this kind of problem, but no package manager can be perfect...
