Premiere fails with keyframes?!
 

Hey all,
I have searched for a general answer to this question, but couldn't find what I was looking for. Here is my specific case: I am trying to edit AVCHD from an HMC150 on Premiere Pro CS4. I'm running an i7 860, 2.8ghz with 8cpus. 4gb ram. The program will freeze up now and then, and some simple editing tools like changing the contrast or brightness with keyframes simply do not work. The freezing up is not a huge problem, I just wait a few minutes and its okay. But the program refuses to display contrast or brightness changes. I can see those edits if I apply them to the entire clip uniformly, but if I use a single keyframe to vary the values, it will not display ANY changes. I don't understand. Has anyone else had this problem?

Also, does this seem like an acceptable rig to run this program on? Will there be a big benefit in performance by upgrading to CS5?
Thanks!!