My estimated payout has gone down by about 50% for the past few days... Anyone have any ideas as to why this may be?
My hashrate has stayed about the same 371Mhash/s.
Take a look at avg block times for the last 5 blocks.

If we find 50% of the block (compared to expected) your payout will be 50% of expected.
If we find 200% of the blocks (compared to expected) your payout will be 200% of expected.
This is what I thought.