Prolly already posted but update drivers? I had a lot of problems with source and some unreal games, updated my drivers and boom. triple FPS. I was weeping with joy.
Nope... wasn't that either. But I could narrow the problem down even further. It has something to do with one of empires textures or sounds. In emp_slaughtered_alt_rc4 there is something in S-bend, close to the waters where NF usually builds their base, which gets me to freeze randomly. Any other place in the map is fine. Also all the other maps are fine aswell.