How do I speed up AE CS6?

Hello,

My AE CS6 is incredibly sloooooooooooooow.  My AE 5.5 is much faster, even with the same compositions.  What do I need to tweak in CS6 to get my performance back - (i.e., to get rid of the lag that I'm getting now when I try to do anything)?

Thanks so much!

Mark