So, I noticed a few days ago that After Effects CC wasn't caching my ram preview(hitting 0) while Multiprocessing was enabled. Just last week everything was fine.
When I hit numeric pad 0 to ram preview, the green bar fills and it previews just fine, but if I hit stop, I lose all my ram previews, green bar is gone and blue bar(disk cache) doesn't appear like it used to. Even if I Cache Work Area in the Background, the blue bar doesn't appear(plenty of space). This seems to be the same case: http://adobe.ly/1IONFWq.
I've already tried disabling disk cache, trashing preference file, purging memory, uninstalling and reinstalling, rebooting, creating a new project. It doesn't matter if it has only one layer(mp4/mov/jpeg/png), or multiples 3D layers, it doesn't cache, the green bar doesn't stick. Turning off Multiprocessing does the trick, but that defeats the purpose of "speed" and I lose too much time waiting for just a preview.
I set 3~6GB(it depends on the project) for other apps and 2~3GB RAM per background CPU. My projects usually contain multiples jpegs(2000px), 1920x1080 ProRes(LT) Videos 23.970fps, Trapcode Particles and Form, around 30~60 seconds and 30 layers. But as I said, even with one layer of any type of file, I lose my ram preview if I hit stop.
Macbook Pro 2012 Intel Core i7 2.3Ghz, 16GB RAM, 120GB SSD/750GB HD
OS X Yosemite 10.10.3
Adobe After Effects CC 2014 13.2
Try clearing all you cache by going to Edit>Purge and select everything
Rick Gerard, thank you for the input, however I've already tried that and it still didn't work.
MP processing is so buggy I would just turn it off.