I recently upgraded from 1.20.8 to 1.23.2 and it now appears the job queue is not running, though manual runs of the runJobs script do work. The wiki debug log has messages saying:
[runJobs] Running 1 job(s) via '/index.php?title=Special%3ARunJobs&tasks=jobs&maxjobs=1&sigexpiry=NNN&signature=NNN'
[runJobs] Failed to start cron API: received 'HTTP/1.1 411 Length Required'
It was suggested on the IRC channel that others are seeing this too and that I should file a bug report, so here it is.