I restarted apache.
Also, I made the following change in /apache/conf/httpd.conf
RewriteRule ^/wiki/(.*)$ /w/wiki.phtml?title=$1 [NE]
# RewriteRule ^/wiki/(.*)$ /w/wiki.phtml?title=${urlencode:$1} [L]
That is, I reverted to the older, simpler form, on the theory that
until the bug in urlencode is worked out, it's better to have a *few*
broken links to things like /wiki/AT&T, rather than have the whole
site freaked out.
There are at least two possible permanent solutions...
1. Fix it so the rewrite works 100% correctly. Since '&' is a legal
character in a url, but not in a query string, the _idea_ here is not a
bad one. Plus, it's nicer in a way for end users.
2. Ban '&' from article titles to simplify our lives. While it is true
that '&' is _legal_ in a url, there's no reason we have to use it, other
than usability for articles like 'AT&T'.
But in the meantime, let's not let the site keep breaking completely.