I’ve had the same problem, with the 16 TB memory glitch reported in Activity Monitor..
I believe the project that I was working from had started to become corrupt. I copied my current sequence into a fresh project, and things went a bit smoother.
Is your entire film in one sequence? Or is it broken into chunks?
16 TB of RAM… we’ll get there someday…
(btw, the system was a dual-core xeon running FCP 5.1.4/ OSX10.4.10)