Wow, that is a far downclock! I know my 4850 drops from 625 to 500 in an attempt to save power. This probably is the same thing, but actually in a meaningful amount. If something stresses the GPU, this should jump up. Have you tried any games yet? If they run (at all, really) then you are fine and this is either wrong or it jumps up to correct. Download the newest GPU-Z to get a second source.