Between this and what the other poster suggested (that my difficulty is set too high) I think I may have pieced together the cause (yours) and the fix (his). Testing now.
Yap. You are right. Your screenshot shows the following:
The speed of your miner is not sufficient to difficulty 128, so you miss a lot of blocks providing 0 shares or providing 1 share(worth 128 shares of difficulty 1) at the very beginning of block calculation. Then this 1 share continuously goes to 0 as more and more new shares comes into round. It's the same as you hop to another pool after submitting first share.
You will be OK with difficulty 1. Set higher difficulties only if you experience problems with your connection to Internet.