MemCache::MemCacheError: No connection to server

hi, all
  after i switched from nginx + thin to nginx + passenger, the error
"MemCache::MemCacheError: No connection to server" always shows up in
the log. i did what the post
"http://info.michael-simons.eu/2009/03/23/phusion-passenger-and-memcache-client-revisited/"
said in my enviroment.rb, but i still get the same error.

any ideas? thanks a lot