From Aghori's blog:
A point in Omnipotence vs Omniscience
In Dawkins' The God Delusion there is an argument showing why omniscience and omnipotence are mutually incompatible. Roughly it goes like this :
If God is omniscient he must be knowing what he is going to do at some point of time (say one year later) in the future. Then he is powerless against changing it. Hence He cannot be omnipotent
As we understand, defining omnipotence and omniscience is a troublesome task at best. And to give it a concrete unambiguous meaning seems impossible. We have tried various tacks of trying to define both the things, none of which works. Ultimately these concepts are ill defined and logically contradictory. Hence they cannot be used to form unambiguously meaningful sentences. So the above proof stands invalid. We are not saying that omnipotence and omniscience are mutually compatible. Just that it doesn't make sense to ask this question. In this respect it is like many English questions which are grammatically correct but meaningless to answer. like - what is the shape of red?