Instance of bug

All searches on the English Wikipedia return no (zero) results. Apparently it's been disabled, but the reason is not given in the server admin log (see https://wikitech.leuksman.com/view/Server_admin_log).

Sample queries:
*http://en.wikipedia.org/w/index.php?title=Special%3ASearch&ns0=1&search=john+howard&fulltext=Advanced+search
*http://en.wikipedia.org/wiki/Special:Search?search=opportunity+mars+rover&go=Go
*http://en.wikipedia.org/w/index.php?title=Special%3ASearch&search=wikipedia&ns0=1&ns2=1&fulltext=Search
*http://en.wikipedia.org/w/api.php?action=query&list=search&srsearch=john+howard

Possibly relevant server admin log entries:

(October 7) 15:00-16:00 robert: switched enwiki to lucene-search 2.1 running on new servers. Test run till tomorrow, if anything goes wrong, reroute search_pool_1 to old searchers on lvs3. Will switch on spell checking when all of the servers are racked. Thanks RobH for tunning config files.
(October 8) 19:02 mark: Upgraded packages on search1 - search6 and searchidx1

Works fine on Commons, see http://commons.wikimedia.org/wiki/Special:Search?search=opportunity+mars+rover&go=Go and meta, see http://meta.wikimedia.org/w/index.php?title=Special:Search&search=test+search .

The Go button works as expected, except if there isn't an exact match on the page title (sample query 2). Then you get a red link and no results (as per above).

Version: unspecified
Severity: critical
URL: http://en.wikipedia.org/w/index.php?title=Special%3ASearch&ns0=1&search=john+howard&fulltext=Advanced+search

Attached: