Media Encoder Flips a ghost Ultra Key frame

Question

First time using Ultra Key - Learning trial by fire.
I've created a short video using a Canon HF G10 and ultra key to layer the video for effect I want.
The Ultra Key is used for about 30 seconds of the 3 minute video and this anomoly only shows up during the ultra key treatment,
The original footage is AVCHD footage and I've thrown a lot of video effect filters at the footage with the Ultra Key.
The project rendered fine first go except I had to adjust the ultra key to prevent background from showing through one preformers black shirt.
After doing this I notice some flickering. What I found is an outline ghost image from the utra key track is flipped upside down and randomly inserted into the final render, also a rectangular monotone transparent block is randomly inserted at times.
Am I throwing too much at my computer or CS5?
I have more than 30 keyframes spread over 4 effects on that track, is that too many or too taxing?
I have rendered this clip a number of times and it seems when I re-open the project the Ultra Key footage isn't rendered so I render it again even though I am just making changes in the encoder. Let me know if you want to see those settings
I am using H.264 at 1080P drop frame and 60 Frames (so far)
This is for playback on a high def television from a computer.
Here's my comuter specs
Processor  2.2 GHz Intel Core i7
Memory  8 GB 1333 MHz DDR3
Graphics  AMD Radeon HD 6750M 1024 MB
Serial Number  C02FC7GZDF91
Software  Mac OS X Lion 10.7.3 (11D50)
You can see a screen capture of one of the offending frames here, I varified that it is
http://fredhunsberger.com/people/White%20Noise%20Mess.jpg
Ultra key settings
Ultra Key Settings
Output - Composite
Setting - Aggressive
MATTE GENERATION
Transparency - 40
Highlight  -10
Shadow - 55
Tolerance - 90
Pedestal - 50
MATTE CLEANUP
CHOKE - 10
Soften - 10
Contrast - 10
Mid Point - 50.00
Any idea why this is happening?
Best, Fred

Answer 1

I'm afraid you're taking it as an article of faith that Ultra Key works fine under all conditions.
A lot of work goes into getting a successful chroma key shot, good chroma key lighting being the absolute most important one.  Adequate distance from the chroma key background to reduce spill is a close second.  Without a screen capture of the original green screen shot, it's tough to diagnose what you did.  But if you just put people in front of a green screen, shot and hoped for the best, I think you're running into green spill problems that won't be solved by a one-step keyer.
You may have to take the shot into After Effects, cut the shot up into various pieces using animated masks to get the keys straight, or you may even have to do some rotoscoping.