I've run a process to find pages in the database with invalid/inaccessible titles and rename them. The ones with invalid characters or that conflicted with existing normalized forms have had 'Broken/' prefixed to their names, and are listed at [[Special:Prefixindex/Broken/]] on each wiki.

These are mostly leftover from old software bugs since fixed, and a lot of them are redirects created by page moves to corrected titles and can now be discarded.

-- brion vibber (brion @ pobox.com)