MediaWiki 1.14 introduced a bug (source) with anchor links: using links like [[#this link]] may create invalid rows in the pagelinks table (empty/NULL pl_title value), resulting in a “Invalid title in result set” result at the top of the wanted pages list (Special:WantedPages).
This issue is fixed in MediaWiki 1.15 but the invalid rows aren’t deleted when running the update script (bug 17751).
This can be solved by running the refreshLinks.php maintenance script (maintenance/refreshLinks.php). Be careful though, this script is pretty CPU intensive. On our wiki with around 2700 pages, it took around 3 minutes (which is fairly longer than the time needed by the update script).
Thanks!