primatte Pro 5

Primatte Pro 5 is locking up my Mac when I render in Final Cut Pro 7. The video card I'm using is ATI HD4870 with 512 memory. Is that card compatible? I've opened the Activity Monitor program while rendering in Final Cut and notice the CPU usage monitor is barely being used along with the system memory is not being used. Not sure what this means except maybe Primatte Pro wants Video card memory?

MacPro dual quad core
Processor 2x3.2 gHz quad core intel xeon, memory 8 gb, 800 mHz, ddr2 fb
Mac OS ver 10.6.8
Quick time player 10 and 7 are on my machine but Im not sure which is being used by Final Cut

If you could shed some light on this question, it sure would be appreciated...Thank you

What do you mean by locking up? Is it crashing? Any alert messages?

What I mean by the computer locking up...when you first press the render keys, it acts like it's going to render fast...the message comes up 2 minutes, then the messages starts extending in time.  My clip of 2 minutes becomes 8 to 9 hours of rendering.  The computer becomes totally unusable while it's rendering. Surfing the internet is about all that can be done while FCP is rendering.  We started up the activity monitor to see if the computer was using CPU or virtual memory and found it wasn't using either.  We tried using compressor, same results. 

Well, it could depend on what you're cutting in - what codec did you shoot/transcode/aquire to work with?