Macantosh Hard Drive fills up when rendering

I am attempting to render an HDV project. I have my hard drive set in the systems settings box. Everything points to my external hard drive but when I start to render, It starts to fill up my main macantosh hard drive.
The Cach, Autosave and render settings all point to my external drive.
Can someone tell me where these files going on my Macantosh hard drive?

In the SYSTEM SETTINGS menu you tell FCP what scratch disk to use, and where to store the waveform, thumbnail caches and the autosave vault.

If you need to find out where this is being saved to, use SPOTLIGHT to look for "Final Cut Pro Documents" and "Capture Scratch."

I checked this already. Here's the weird thing. Even though my settings are set to an external hard drive, When I render the timeline, I can see my macantosh hard drive filling up. But there is no folder showing there.

One thing that may be causing it is that my render files are on external drive A and I am rendering to external drive B. Could this be why?

I can't convert to an MPEG2 file until I figure this one out.

Please advise.

This is getting serious. How can my macintosh drive be filling up yet all system settings are pointing elsewhere? And, there is no render or scratch file on my Macintosh main drive that I can find or see? This is very virus like. Any suggestions out there? I am attempting to render HDV to high quality YUV in my sequence settings as well. Could this have an effect?

Please Advise