I've had to stop my cga p2pool server twice to re-download the blockchain. It keeps getting hosed. Something is wrong with the daemon or network. I'm going to keep it down until there's a fix.
There has been issues with the P2pools, check the settings for the protocol version, we have changed it a few times to fix forking issues, your protocol version should be "70006", of coarse I don't really know the specifics of p2pool but it may be the problem.