Help: "Fatal error: Call to a member function isListed() on a non-object"
Fragment of a discussion from Extension talk:User Merge and Delete
hmm, what version of MediaWiki are you running, and which version of this extension?
If you're running a recent version of MW (1.13+) try downloading the development version from here:
http://upload.wikimedia.org/ext-dist/UserMerge-trunk-r93008.tar.gz
