As it says on the tin. I think $page might need to be lowercased in editpage.pm. Workaround until then is to change the setting to 'discussion'.

?version 20111106 says: "Fix handling of discussion page creation links to make discussion pages in the right place and with the right case. Broken by page case preservation feature added in 3.20110707." So I think this is probably done? --smcv