Unfortunately there is no way to avoid this problem for me - I need to scrub with the audio as I am Synching the animation with an audio track.
Also, deadline is today, so there is no other way to deal with this besides opening and closing AE...
Those errors point to an incompatible plug-in or CoDec.
thanks for your reply,
Not so sure about the plugins as I do not have any external plugins installed.
As for the Codec, I have no idea how it would influence the workflow.
This problem does not occur while working on lighter AE files.
I've experienced the "RAM preview needs 2 or more frames to playback" error quite often in the past but I can say it could be related to the low RAM on my old mac but I've never experienced such a persistent problem like this one, even our new Mac Pro can't handle it.