Yesterday I was having such trouble and it turned out it was as simple as installing an update.
So what I have tried to do myself and failed poorly (crashed 2 test sites trying).... Is to come up with an add-on which will check XenForo for the update.
Important - Not looking for it to self update. Just check for updates.
phpBB had this built-in
vBulletin had an add-on http://www.vbulletin.org/forum/showthread.php?t=255054
Word Press has this built-in
So I would imagine someone would know how to do this (better than I).