I'd like to add that I was completely wrong about my issues. I thought it was my slow CPU miners, but it can't be because as everyone else said, the diff should have just increased variance, but I switched to Middlecoin (which is locked at 1024 diff) and I'm getting no REJECTED shares. So sorry for that confusion, but I only seem to have this problem on Wafflepool, which is too bad. I've tried multiple Wafflepool servers, but just get continuous REJECTED shares. I'll keep trying, I really want to mine here. Thanks to all for the information and suggestions.