As of today, whenever I take control of an actor the game slows down substantially. It isn't because my computer is crappy, the game has played fine in the past and I have 4 gigs of ram, a 512 mb video card, and a 2.4 gig dual core processer. I tried reinstalling the game and it didn't help. Does anyone know what might be the problem?

Running any mods? Have you tried running the game without mods?
Sure it isn't a speed issue? You can speed the game up with '2' and slow it down with the '1' key.

I am running mods, but I was running them before it happened. It might have been a game speed issue, I'll check that out. Thanks.

CC often just doesn't like certain computers.
But I can see something that could slightly improve your performance.
Go into Task Manager and go to the Processes tab.
Right click on the processes one by one, changing the Affinity of each one to one of your CPUs only.
Then change the Affinity of Cortex Command's process to the CPU that none of the other programs are using.
CC doesn't do multi threading, so doing this should mean that it has a nice processer all to its self, hopefully increasing performance.