I get "Problems communicating with bitcoin RPC" errors after a short while. Does it mean that you restarted the pool, or is it something else ?
The pool will probably see
many restarts in the first 24-48 hours of its lifetime.
Additionally, I am currently using python's BaseHTTPServer, which seems to sometimes pause for several seconds before giving up on a socket, and processing more. As soon as this is turned into a multi-threaded server, that should not be a problem anymore.