I had a problem with the camera projection with an image.
Tried some things. Didn't work. Searched and found some threads.
This one for example
http://www.planetside.co.uk/forums/index.php/topic,2983.30.htmlMaybe my fault i don't know, still couldn't get it to work.
In the end i used the very basic way below. Not sure if this solution is here around already.
If not and you stumble on this kind of problem maybe it might help.
Use "Throught Camera" settings with the render camera.
Don't change anything in the image map node or camera node.
But change the image map canvas size (not image size) as you see below to 1:1 scale.
You might get unneeded shadows etc in the upper and lower side if you use it this way of course.
Just put in those areas what will suit you.