Compressor and MC color issues

DOES COMPRESSOR AND HD AVID MC 5 WORK IN THE SAME COLOR SPACE? When I run either a reference movie or a Same As Source QT exported from DNx36 or DNx115 through Compressor I get a massive gamma shift. Whats up with that? Does it have something to do with RGB vs 601? I use Cram with Compressor, and all of the QTs made with the Apple Movie Trailer presets suffer a massive gamma shift, making everything too dark. Sometimes it varies when I open them with Quicktime 7 instead of X, but not always. I'm baffled. How can I make sure to end up with the same color values I have in my reference once I run it through compressor? I understand that anything "compressed" is inherently going to be different, but my blacks all all far too crushed to be explained by mere compression.