FCP Rendering Issue

So I'm trying to figure out why a FCP project renders quickly on the computer I usually work on, but MUCH slower when I bring it to another Mac. The entire project is saved to an external LaCie drive and brought to another Mac. But when the project is loaded, and all the clips are connected, everything needs to be rendered and renders painfully slow. All the render settings seem to match on both Macs. I understand that if I work off the external hard drive it will be slower... however even if I do this on the computer I normally work on the render speeds are still much faster than on the Mac in question.

Can anyone add any insight to these render issues? Why so slow and why does everything have to be renderd again on the second Mac?

Difficult to give you any clues without having the full specifications of both Macs (processors, ram, HD, SSD, OS, external drive interface etc) or indeed which version of FCP.

Are you definately taking the render files over on the external drive? Are the settings in Render Manager identical?

Here's what I know office hand... both versions of FCP are version 7. Main Mac is a newer Quad Core tower running Snow Leopard.. second Mac is an older MacBook Pro also running Snow leopard... all render settings seems to be the same howeveri j would have to confirm that. As far as the projects goes the entire project is saved in a folder along with all the captures, renders, graphics files, etc.

What should I be looking for that might cause this issue?

And both connecting to the HD via FireWire 800.