Well the RAM is definetly working, but the first time I had this message was when i was rendering a file that was thousands of pixels high and wide. Now I seem to get it whenever I am doing any kind of animation, just re-rendering a quicktime seems to be ok.
So, it only seems to be when there are a few effects and filters in use that it struggles.
I’ll try the secret preference and purge the RAM while rendering, then if it continues i’ll get back on here!