Severe server lag?

If you open up the task manager during a lag spike, you'll see that Cipher's usage goes up significantly. I've had it go up to 45% during one of my spikes. I set it to low priority and gave it one processor (versus all of them). Doesn't stop the lag spikes, but they're less severe and less often.

When I try to set the priority on it, it says I don't have permission to do so o-o