I am working on a scene with more than one renderlayer. I have a background, and a charakter that is overlayed. When I enable Mist for my scene and than add the charakter with alpha over, the charakter is transparent and has not full opacity. I don't think this should work like this. Disabling the mist the everything works fine again.

I have recreated this problem with a simple blend.
Also I found thread on Blenderartist.org with a similar problem.

http://blenderartists.org/forum/showthread.php?p=1539163