dogepet, the pool is working on its first block at the moment.  Having said that, you'll find it difficult to get a share at 300kh/s.  What gpu are you using?  Have you tried using bfgminer?

Welcome to the pool, Cosmos.  Whilst p2pool increases in speed from virtually zero sometimes rejections can get high.  We're cruising at a just under 1Th/s at the moment so hopefully rejections should be better now but if you're still getting a high rate please do say.  If you can post your command line or config you're using for mining it may help.