I learned long ago never to do a Yum Update.
FreePBX and Asterisk have far too many working parts that require certain versions of certain programs, i.e. PHP, MySQL, Asterisk, etc.
Yum Update will update you to the very latest version of everything, and often break everything.
My recommendation would be to reinstall. If you're using the Distro, then use the update scripts if you want to update, or limit your use of Yum Update to very specific apps.