We’ve found some issues with our memcached cluster, which we’re working to resolve as soon as possible. Symptoms of this are slower sites, and sometimes pages that will return a “504 Timeout” page. 

Sorry for the issues, we’re working to resolve these issues ASAP. 

Update February 12, 2013 8:46 PM: The problem was fixed at 7:30PM CST, we’ve been monitoring the situation for the past hour, and things have been stable. We consider the issue resolved.