I have just installed PHP5 Memcache on my Xubuntu dev machine and every page loaded was returning me an annoying error of Memcache connection error.
Warning: Memcache::connect() [memcache.connect]: Can't connect to localhost:11211, Connection refused (111)
When after you tried everything it still doesn’t work, you got to research for something that will actually correct your issue. With that in mind I found this great post that shows a very easy trouble shooting for fixing the connection error with Memcache.
The post is related to installing, but the last 3 commands will help you do a full troubleshoot with your current Memcache configuration.