Thread:Project:Support desk/help with this: Fatal error: mcrypt create iv()/reply (12)

Well work around is to use 1.18.1 (note .1 not .2. It can be downloaded from http://svn.wikimedia.org/svnroot/mediawiki/tags/REL1_18_1/phase3/ . If you don't have an svn client to download it though, it will be a pain to download). Note however this is missing some security fixes, and is insecure (The issue you're experiencing is the patch to make stuff secure gone slightly wrong).