Thread:Project:Support desk/Shoutbox-Extension wont work/reply

Try using the version at http://svn.wikimedia.org/svnroot/mediawiki/trunk/extensions/ShoutBox/ instead.

The version you have probably has a line like $wgMessageCache->addMessage( ..) which support was dropped for sometime around 1.18 I think (It's very unclear why extensions were doing things like that, it shouldn't have been needed really ever)