Thread:Support/About MediaWiki:Viki-error-content-namespace/en/reply

No, it is actually fetching the content namespaces themselves (the integers). VIKI renders links between pages, but only pages which belong to namespaces that are designated as content namespaces. So for example, if your page links to the Special:Version page, and you haven't designated the Special namespace to be a content namespace, then VIKI will not render that link.

To do this, VIKI needs to make a query to determine what the content namespaces are, so it can compare any pages to be rendered against this list. If this query fails for any reason, the error message states that this content namespace fetch has failed, and VIKI defaults to assuming that only the main namespace (NS_MAIN, or 0) is a content namespace.