Removing the header S-O-L-V-E-D it! Man, I'm sooo happy!
I made your change to my side, installed python 2.7.3 64-bit (windows) and all the associated apps needed for p2pool and fired it up.
The dupe message is definitely gone.
Now, however, cgminer on my main miner (4x7870 = 2.6g/h) is complaining non stop about p2pool not providing work fast enough. I think if my phoenix miner (4x5870 = 1.6g/h) had a better UI, it would be complaining too.
I'm not sure this is an improvement.
M
So I'd guess your p2pool setup is very slow or has poor network connectivity to your miner since it really should be a local miner talking to a local p2pool and that REALLY should be fast?!?