FCPX Render - Machine starts dragging

So I noticed that my machine started really dragging as I rendered a project file. I opened Activity Monitor and saw that before I started the render I was at 2GB used (out of 12 total) memory usage, and as the render goes along my memory usage went to 11.8 Gb used. I also noticed that when I exited FCPX it does not free the memory for the most part (went down to 10.6 GB used). Started looking around and noticed this post.

support.apple.com/kb/HT4722

Where it was strongly recommended not to install FCPX on same partition as another version of Final Cut, which I had done. (Why didn't it detect that and warn me!)

I booted up another MAC that had never had FCP installed and put FCPX on it rendered the same project and the memory usage never gets above 3.1 GB.

Other factors,

On the initial machine, my source files and rendered files were on the same partition. On the new machine, I copied my source files to an external drive and rendered to the internal partition. Not sure this would effect memory.

Initial machine was fresh install of Lion
Other machine was fresh install of Snow Leopard

FCP X and FCP 7 don't share resources at all.

Are you running FCP X 10.0.2?