that could be caused by a pile of background processes slowing down your system aswell, just a heads up.
my CC only lags occasionally when nothing is happening, usually its only more than one large actor gibs..

What do u mean by, usually its only more than one large actor gibs..

there was supposed to be a "when" in there, as in

for example, my CC experiences lag usually when a few drop ships collide.

u see that's why i find the lag wierd, i can have a few dropships crashing and theres only a slight bit of lag, still easily playable but it lags randomly e.g walking down bunker with nothing happening, the dropship crash and fine, other times other way around?

mmn, that happens normally to me, too, for no reason. CC is a flippant bastard of a program.

dam, does this mean I have to remake my map?

oops that last post was meant for a differant forum reply, sorry thought i was in map making one lol

I've been getting this exact same problem for a long long while now.
I've Tried Reinstalling, Re-downloading, Restarting, System Recovery and A lot of other things beginning with R.
I've Tried everything suggested and if anyone has any other suggestions that'd be great.