There is 2 type of bitcoin adresses prefixes .
Originally those starting with 1 is Pubkey hash (P2PKH) addresses . This with 3 is Script hash (P2SH address).
P2pool code originaly accept only P2PKH address for mining user . Similar to MUE P2PKH address start with 7 and is accepted by p2pool code as user. P2SH address isn't accepted on any p2pool mined coin. P2SH addresses are generated with web wallets .
in practice that 5* addy is accepted as user but pool can't grant any shares.
here it is: i mined for 18 min on e-pool with 51EFnkwc6cMEqRBpMFyEWcyk97yb91Cnek,
during that period pool found 2 blocks, then i switched to 7DBX9Du4wDKXy5yv2pqTFyWiimLr4x6xSf.
7* addy immediately receives some shares even with no blocks yet, 5* addy - none.
i saw similar shit on lulu's dime pool.
http://i.imgur.com/aAKlxaw.pngGood research.
We will dig a war axe.
P.S.
As I also spoke with my miner everything is all right and tomorrow he awaking to work again and I added capacities "a little" now there will be 350 Mh/s