On my MediaWiki 1.20alpha (r114161) I added some new Interwiki definitions such as geocache = http://www.geocaching.com/seek/cache_details.aspx?wp=$1
I found that links on my pages like [[geocache:GC3GAJZ|GC3GAJZ]] which uses the new Interwiki definitions were not rendered as http://www.geocaching.com/seek/cache_details.aspx?wp=GC3GAJZ
not even - after &action=purge - setting $wgCacheEpoch = '20030516000000'; - Ctrl F5 in my browser - dummy edits
Any idea, what is wrong ?