Galera installation tests on CentOS 5 in buildbot fail with an obscure "Lost connection to MySQL server during query" error on enabling wsrep_provider:
http://buildbot.askmonty.org/buildbot/builders/kvm-rpm-centos5-x86/builds/2248/steps/test/logs/stdio
http://buildbot.askmonty.org/buildbot/builders/kvm-rpm-centos5-amd64/builds/1981/steps/test/logs/stdio

I did some digging and it turned out that the actual cause is strict SELinux settings which Galera cannot deal with (it's documented in Galera FAQ: http://www.codership.com/wiki/doku.php?id=faq#qnothing_works_damnit)

In my experiments, it was enough to switch the level from Enforcing which it is in the VM now, to Permissive at runtime using setenforce. Setting the level permanently and rebooting the machine also helped, of course.

If the level is set/kept high on purpose, please consider a conditional setting it to Permissive at runtime for Galera tests (if you do so, please make sure setenforce comes with the full path, it's not on the PATH). If there is no particular reason to have it Enforcing by default, maybe it's easier to reconfigure it permanently.

I was checking 64-bit build, but I suppose the reason of the failure on x86 is the same.