Mini Freeze

Hi

I have been playing the game for a few hours now and im getting stuttering or mini freeze if u will it freezes for a second or 2 then fine for 4 or 5 seconds then freeze, this will happen after iv built and explored most of the map. Im playing a big big map but iv never had problems like this on any other game except "civilization v" but that game has memory leaks.

SPECS: AMD Phenom II X4 965 Processor 3.40 GHz
       6GB of ddr3 ram
       64-bit windows 7
       ATI 6950 HD Graphics Card

Drivers all upto date. Tryed with AVG off, and all backgrond processes off.