Thread:Project:Support desk/Problem using Extension:Interwiki with MW 1.18/reply

Are you really using the 1.17 version? It says on Extension:Interwiki to use the extension as of for MediaWiki 1.17 or MediaWiki 1.18.

In the extension code at r92408, there is no call to  in   on line 165. About 5 versions before that revision it was replaced with.

So it looks like you're not using "the 1.17/1.18 version".