What does your bat file look like? It could also be an issue either with the pool or Poloniex. I know that I never mine directly to an exchange address. It is much safer in my mind to mine to a personal wallet and then transfer it to the exchange.
I fixed it lately. I just copied a configuration "sentence" from someone in the Claymore official thread and replaced his username with mine and his password with mine. He was using zec suprnova cc pool and I love that pool so it is working now, saved this configuration in my D: drive and USB so I have it ready for many other mining boards I intend to build.
