I didn't think it was the pool either, but I've tried everything. I switch back to eligius / btcguild, and instantly my hashrate goes up by 10% plus. I have newest firmware. Somehow I'm doing something wrong, no way all the people mining on p2pool are giving up 10% plus from their hashrate.
The hashrate isn't swinging a lot, its just stuck at about 10% lower than should be, which is sort of big deal. I get the expected amount for the reduced hashrate. I really want to mine on p2pool but this is a major roadblock.
Although I never owned a miner in my life ecept a few block erupters last year, Have you treid to restore it to factory firmware? Is it possible then reflashing the newest one.
I don't know if you want to try that.