The low you have listed for 10/31/07 is 808.8, but CME has 811.4; http://www.cme.com/html.wrap/wrappedpages/end_of_day/daily_settlement_prices/er2.html?h=1

Of course this gives a different PP, I have a central PP of 826.0 using the CME low.

Thanks mwald! I have corrected it and new figures have been generated which match what you have.

I checked a few different sources and I can see where the error came from.