On a simple hello.tex like this:

\documentclass{article}

\begin{document}
Hello, world!
\end{document}

xelatex and luatex crash because they were compiled with an older zlib (I found the description of the reason somewhere on the web, in a mailing list):

$ xelatex hello.tex 
This is XeTeXk, Version 3.1415926-2.2-0.999.6 (Web2C 7.5.7)
 %&-line parsing enabled.
(Fatal format file error; I'm stymied)
$ luatex hello.tex
PANIC: unprotected error in call to Lua API (zlib library version does not match - header: 1.2.7, library: 1.2.8)
$ rpm -qf /usr/bin/xelatex /usr/bin/luatex
texlive-xetex-2008.0-alt0.15.5
texlive-base-bin-2008.0-alt0.15.5
$ rpm -q zlib
zlib-1.2.8-alt1
$ 

To avoid such errors, an explicit dependcy on the version of zlib should be set in the RPM package.

(For them to work, they should be rebuilt now, anyway.)