Thread:Extension talk:UserAdmin/Fatal error: Call to undefined function wfLoadExtensionMessages() in .../wiki/extensions/UserAdmin/SpecialUADMBase.class.php on line 59/reply (2)

Had the same problem with the upgrade; you have to comment out the call to wfLoadExtensionMessages as explained here: https://www.mediawiki.org/wiki/Thread:Project:Support_desk/wfLoadExtensionMessages%28%29_removed_from_1.21.1%3F

But the UserAdmin still doesn't work; I'm getting the "No special page" error if I try to do anything.