[Zach Westerman]

This problem still exists, (so hopefully this benefits other users trying to find the solution to this.)

I found a work-around by toggling the caps lock key on and off

It used to be that pressing the Caps Lock key would turn off your video preview and allow you to cache frames quicker if things were slowing down. After Effects no longer appears to function in that manner, however the caps lock key will still give you results. Sometimes all you have to do is push it once and the frames will start caching. Often times for me though, I have to keep pushing it on and off until I have enough frames cached to work.

I realize this is not ideal, but so far it’s the only way I found to actually speed up the process of caching previews. You could also try a newer version of after effects to see if the bug is corrected. (I would keep your old version installed though as often times more things are broken in the newest versions)