How can I get my renders to work in the background?

Question

Hi,
I installed After Effects pretty much without changing anything, so the settings are more or less default.
I'm using a Macbook Pro with OS 10.6.8 and After Effects CS6
I have enabled media and disk cache, max disc cache is at 100GB and I have an external drive (with 900GB spare) as the volume selected beneath that option. My internal SSD has not much spare on it. I previously had the internal SSD as the disc cache and still had this same problem.
My project is 1920 x 1080 25fps - And I'm trying to render to Quicktime. I've tried rendering to stills and then outputting to Quicktime (so as to have less computational effort), then running them through but the same problem persists.
If After Effects is the application in focus the project renders fine.
If After Effects is not the application in focus - ie. I work with it rendering in the background, the 'FINISHED' sound plays and the render is cut short a short while after I started working in another program.
The project render time is about an hour, so it's not really convenient.
I've googled extensively and posted this here before and no solution.
Please help.
Toby
ps. ADOBE: Don't mean to be rude, but is there some fix for this text entry box where the cursor randomly jumps to a previous line? - still broken guys!

Answer 1

Hi Todd,
Thanks, I've now installed the updates. Unfortunately the problem persists and furthermore, AME does not go the distance with rendering the full project, dropping the process after around the 5-8% mark (on first and second try).
I can render the project successfully if AE is left unattended in the 'foreground'
Please find attached screengrabs of my system profile and current AE settings (Disk and Cache settings were changed recently from having 100GB disk cache on external USB3 drive - still same behaviour).
I notice there is no error log produced from AE as it seems to think the render is successfully completed. Please advise if I can produce a log to help troubleshoot this problem, as it seems AME does not provide a workaround.
Thanks in advance.