Funny you say that, if I take the addresses and enter into my
stats page I can see that the hashrate for all of them a pretty stable over time (7 days) and should in no way have anything to do with different balances, this is
ALL server differences that should be taken care of asap.
to me, 'pretty' stable is not stable. you have a ragged sawtooth, not a line. you're seeing the peak of one user's sawtooth, and the valley of another.
e.g. in your last 24 hours, i see a peak of up to 3.0mh, and a valley close to 2.1mh. that is a max/min difference of 0.9mh. everyone has this same flux in their hashrate as returned by the middlecoin servers.
e.g. take a look at your bottom 'pretty' stable graph of accepted shares in the past HOUR alone: at times you have over 150shares/min, and at other times you have 0shares/min. again, a 'pretty' stable graph is not stable.