system requirements help.

[overweightninja]

I tried it, didn't help. seems like the slow downs are trigger by selecting units or cities, especially units with the green highlight indicating movement area.

I haven't defrag for over a year now, will try it tonight when I go to sleep.

If that's what I think it is, it happens frequently but is very easy to fix (for a short while anyway). I swear a lot of the people talking about "lagging campaign map" and stuff mean this but I rarely see this solution presented .
Just select a unit in a settlement (usually works with field stacks too but just to be sure...), move them just outside, everything should pick back up again. You can then just put the unit back in the town or do whatever else.
System specs sound fine if its running cleanly, keep AA off and I can see that rig coping okay with medium settings.
Hope that helps
Cheers