Hi Kevin – thanks for your message. This has been driving me mad!
I am running OS 10.6.2 on a single screen (MBP 2.8, 4GB Ram). FCP version is 6.0.6. The project and media are all running from a LaCie Rugged external drive over Firewire.
The FCP project contains 1920 x1080 Quicktime Movies (captured in from HD cam) and also 1280 x 720 Quicktime Movies (from a consumer digital camera). Project also has subtitles and makes use of the Crumplepop photo plug-in.
Cheers
Simon