I hope you solve the chroma-key issue.
I use it all the time in PD and its OK.
I have done lots of green screen and blue screen work and here are my tips for getting the best.
By the way here is one video done with green screen under a battery of homemade studio lights. 6 fluorescent 75W 5 foot tubes for the background and six pink pearl 100W lights in a semicircle around the musician.
http://www.videocentricity.net/view/86/tommy-a-blue-mood/
Its VERY difficult to get good FLAT lighting of the same luminance all over.
Its the change in luminance you are seeing as black when you apply the chroma setting.
heres a video
http://seemyworldonvideo.com/view/664/paris-bleu/
made on a blue screen background where the lighting was flat cloudy daylight from a window lighting both the subject (me) and the background. There were NO room lights at all. (The window was behind the camera)
I have also used a dark red blanket under daylight. The color does not matter. The lighting is everything !
Typically when doing green screen, your background isn't perfectly lit so the green is not the same luminance all over. When you do the chroma-key you can get dark areas usually further away and below where the eye-dropper was touched.
So, 99% of the problem is the human eye can't detect small changes in luminance across a lit backdrop, so it all looks OK until you do the chroma-key. I suggest less is better. Dont try to overlight the backdrop with lots of artificial lights, thats where flaring occurs and the eye cant tell. I even tried using a Weston light meter to measure but the change is so slight, and the effect so visible.
Best of Luck
If you can't solve the problem - Change the problem