It's a memory function, in this case. (prob. 85%) How much RAM are you running, and is it DDR? 256 MB is enough for most scenes, but more is ALWAYS better with RAM. Big scenes still balk at me... One thing that often works, sir, is to save it as a different file name. Then just delete the original and rename the new one, if necessary. That's been working for me on my 127MB Hunting Cabin Scene, which I thoroughly loathe now, with all my heart. Give it a whirl, save it under a new project name...