Read the part about new memory handling performance here:
You may want to check the box that says "Reduce Cache Size When System Is Low On Memory" under your memory and multiprocessing settings
I really need to fix this problem ! Can I get the previous version from CC back?
Installing CC 2014 (version 13 of AE) does not remove the older version (version 12). If you've uninstalled it, you can reinstall it. Adobe has committed to keeping older versions of programs available and you can even download CS6 still (version 11).
Thank, I hope it will solve my problem but I can't find a place to download the CC version 12?