I'm pretty new to After Effects and my friend has this problem which i dont know how to fix.
Everytime he RAM Previews his footage, it plays just like normal when its done rendering.
The problem is that if he RAM Previews it again, it renders it from the beginning again, although
nothing has been changed. I do not have this problem. We are both using CS6.
Nobody can tell you anything without proper system info or other technical details like what comp settings, effects used, keyframes and so on. Usually this happens with flakey effects or specific audio stuff involved, since this stuff uses hardware acceleration and misconfigurations there make it go boom...