Hate to be the necrohippoflogaphiliac here, but I'm still getting really high rejects (even after the tweaks you did), also my hashrate is all over the place when I know my CGRemote is showing a cool 2.0 MHash.
Please take a look
http://www.clevermining.com/users/1M6ZozLvZoRhD6NLhtfcVB2aWcgtZhUG8w\Ideas? This is a rig I've mined with for months, and I've never had a high reject rate like this.
Pools "measure" hashrate via shares accepted. Accepted shares have variance, so your hashrate will flux. Doesn't appear your reject rate is all that different than the pool's. What is your avg reject % on cgminer?