[UPDATE: Note that this bug is listed as fixed in the upcoming After Effects CC 2014.1 (13.1) update.]
The After Effects team are investigating a bug in After Effects CC 2104 (13.0) where a memory leak occurs while scrubbing audio (holding down the CTRL or Command key while scrubbing). This memory leak can eventually consume all free RAM, which can lead to the warning message “After Effects error: RAM Preview needs 2 or more frames to playback” when you try to initiate a RAM preview.
While we investigate this problem, you can avoid the bug and memory leak by not scrubbing with audio. When the problem occurs you can resolve it by closing and restarting After Effects.
Using the Edit > Purge commands do not affect this problem, as the leaked memory is not tracked by the image cache. Leaked memory is memory that an application consumes but does not return to the operating system as free memory when it is finished with it, preventing re-use of that memory. In Activity Monitor on Mac OS or Task Manager on Windows, you can track the amount of free memory on your system and memory in use by After Effects.
The “RAM Preview needs 2 or more frames” warning means that After Effects can not build a RAM Preview because it can’t build a second frame.This may because your composition or work area is only one frame long, or as in this case it can happen when there is not enough free RAM to build the second frame. High resolution compositions and 16bpc or 32bpc color have higher memory requirements and therefore may experience this warning more frequently.
To discuss this bug, please post in this thread in the After Effects User to User forum.