The wiki seems to be in trouble. On the SiteMap, all pages look as if they don’t exist. It turns out the reason was a weird page file:
/org/org.emacswiki/htdocs/alex/page/other/.db
This page had no name, and therefore the pageidx file looked as follows: page_a 1 1 page_b 1 page_c 1 etc. The empty space between the two consecutive ones gave it away. Strange bug. Yesterday emacswiki.org was undergoing kernel upgrades, so perhaps some crash left such a file. It should be possible to fix such a situation, however. Perhaps the code generating the index file should check for illegal pagenames, too. Well, perhaps only really troublesome names such as no names or names with a literal space in them.