I am using After Effects CS4 and my operating system is an Imac OS X Leopard. I believe it has 4g of RAM. There is an error message that directs me to the preferences drop down menu to adjust the memory and multiprocessing options and to adjust RAM to leave to other applications. The error message also recommends to select the enable disk cache option under media and disk cache menu.
By fragmenting I mean the project is being rendered correctly up until the last few seconds and the last part of the project disappears. It acts like it randomly chooses what it wants to render at that last section of the project. The project is a hallway if that helps you visualize what I’m trying to say. The last section is a couple of doors and the walls, floor and ceiling, of course. I hope this helps.