Stalling:Error in background rendering so switching to foreground rendering after 0 frames completed

Question

Our facility is running AE CS6 ver 11.0.0.378 on 8 core Mac Pros with 32 Gb ram running OSX10.6.8
using Thinkbox Deadline 5.2 for distributed rendering to other 8 Core Mac Pros with 32 Gb ram.
The issue is that we are in crunch mode trying to deliver 4K comps (soon to be 8k comps) and we are experience substantial
delays 10-20 minutes after the AERENDER starts, but before it starts doing any fruitful rendering.
We are reading from and writing to Quicktime movie files (which normally works just fine for us) and thus the entire frame range needs
to get computed on a single host.
The symptom is that many comp jobs (but not all) stall for a while with no apparent actibity before spitting this messgage, but then happily
and swiftly complete each frame in a second or less with no errors:
0: STDOUT: PROGRESS:   There is an error in background rendering so switching to foreground rendering after 0 frames completed out of total 576 frames.
0: STDOUT: PROGRESS:  00001 (1): 20 Min, 16 Sec
0: STDOUT: PROGRESS:  00002 (2): 1 Seconds
0: STDOUT: PROGRESS:  00003 (3): 0 Seconds
0: STDOUT: PROGRESS:  00004 (4): 1 Seconds
0: STDOUT: PROGRESS:  00005 (5): 2 Seconds
0: STDOUT: PROGRESS:  00006 (6): 1 Seconds
Given that the delay, seems to be related to the number of frames (350 frames creates a 10 min stall and 576 frames creates a 20 minute stall), it seems like it's trying to do something for every frame in background mode, before it gives up and does them quickly
in foreground mode. During this time, there doesn't seem to be any signficant CPU or Network or IO activity. I looked for command line args that might force AERENDER to foreground mode, but didn't find anything.
Here's what the digested submission args look like.
0: INFO: Startup Directory: "/Applications/Adobe After Effects CS6"
0: INFO: Process Priority: BelowNormal
0: INFO: Process Affinity: default
0: INFO: Process is now running
0: STDOUT: PROGRESS:  12/6/12 10:37:54 AM PST: Starting composition  sc20_assem_R_v57 .
0: STDOUT: PROGRESS:  Render Settings: Best Settings
0: STDOUT: PROGRESS:  Quality: Best
0: STDOUT: PROGRESS:  Resolution: Full
0: STDOUT: PROGRESS:  Size: 1200 x 860
0: STDOUT: PROGRESS:  Proxy Use: Use No Proxies
0: STDOUT: PROGRESS:  Effects: Current Settings
0: STDOUT: PROGRESS:  Disk Cache: Read Only
0: STDOUT: PROGRESS:  Color Depth: Current Settings
0: STDOUT: PROGRESS:  Frame Blending: On for Checked Layers
0: STDOUT: PROGRESS:  Field Render: Off
0: STDOUT: PROGRESS:  Pulldown: Off
0: STDOUT: PROGRESS:  Motion Blur: On for Checked Layers
0: STDOUT: PROGRESS:  
0: STDOUT: PROGRESS:  Solos: Current Settings
0: STDOUT: PROGRESS:  Time Span: Custom
0: STDOUT: PROGRESS:  Start: 00001
0: STDOUT: PROGRESS:  End: 00576
0: STDOUT: PROGRESS:  Duration: 00576
0: STDOUT: PROGRESS:  Frame Rate: 23.976 (comp)
0: STDOUT: PROGRESS:  Guide Layers: All Off
0: STDOUT: PROGRESS:  Skip Existing Files: Off
0: STDOUT: PROGRESS: 
0: STDOUT: PROGRESS:  Output Module: APR_422HQ - Millions
0: STDOUT: PROGRESS:  Output To: /Volumes/Renders/Scenes/20/sc20_assem_R_v57_r1_2k.mov
0: STDOUT: PROGRESS:  Format: QuickTime
0: STDOUT: PROGRESS:  Output Info: Apple ProRes 422 (HQ)
0: STDOUT: PROGRESS:  Output Info: Spatial Quality = 100
0: STDOUT: PROGRESS:  Include: Project Link
0: STDOUT: PROGRESS:  Output Audio: Off
0: STDOUT: PROGRESS:  Channels: RGB
0: STDOUT: PROGRESS:  Depth: Millions of Colors
0: STDOUT: PROGRESS:  Color: Premultiplied
0: STDOUT: PROGRESS:  Resize: -
0: STDOUT: PROGRESS:  Crop: -
0: STDOUT: PROGRESS:  Final Size: 1200 x 860
0: STDOUT: PROGRESS:  Profile:  -
0: STDOUT: PROGRESS:  Embed Profile: 
0: STDOUT: PROGRESS:  
0: STDOUT: PROGRESS:  Post-Render Action: None
We're under the gun to get this production delivered, and these delays are killing us. I worry when we switch to 8K comps
that the "fruitless delay time"  will just get longer.   
I'm currently trying to correlate the plug-in assortments in effect for the shots that exhibit this behaviour. Clearly in "foreground mode" the machines are capable of rendering the shot quickly.   We've speculated, that posibly some plugins may be GPU or OpenGL accelerated (these machines have ATI Radeon HD 5770 cards) despite the fact that AERENDER probably doesn't require special graphics cards).
Anyone have any ideas, especially if there is some way for force the foreground mode from the start?
Regards,
Jay Production IT Support.

Answer 1

Just to follow up, Our compositing supervisor was still convinced that running with MP was the way to go, so I worked
with him to run some benchmarks on medium and heavy shots that we determinied would trigger the issue in -MP mode.
The test scene was about 50 frames in length, and we ran it on the same hosts with -MP on and -MP off, and also ran a 
version of bundled frames (10 frames per host/task) and another where we did all 50 frames on a single host (with and without MP).
Interestingly, in every scenerio of these 4 cases, the version with -MP on, was 2-15% faster (despite the 10-11 minute delay at the start in MP mode).
His conclusion was it's still faster with -MP mode ON, and requested that I continue to explore for patches or theories how we might get around the delay.
Have read links:
http://forums.creativecow.net/thread/2/1025525
http://helpx.adobe.com/content/help/en/after-effects/using/memory-storage1.html
Regards,
-Jay-