I had a similar problem with updating the cache, and I fixed it with the MagicNoCache extension (http://www.mediawiki.org/wiki/Extension:MagicNoCache). This extension creates a magic word (__NOCACHE__) that disables the cache for that page.
You can find more info on purging your cache at the Wikipedia:Purge page (http://en.wikipedia.org/wiki/Wikipedia:Purge).