Hi folks,
We had issues with our old fallback media storage server (the one we're replacing on Monday [1]), causing cascading issues on the cluster, starting around 5PM UTC. The outage affected editors, as well as readers viewing uncached pages. Everything should be back to normal.
Thanks to Domas/Asher/Ariel/Leslie/Jeremy/CT and anyone else who helped.
Erik
[1] http://lists.wikimedia.org/pipermail/wikitech-l/2012-October/063704.html