Well, my 5d mark ii now shows, almost always, the bottom half of the screen black.

I did manage to get it clear twice during the day. After I turned off the camera or took a lens off, it went right back to half black. It reminds me of seeing a photog's flash/shutter speed off.

Is this my mirror? Has anyone had this problem? Any idea how big a deal this will be when I send it in to CPS?

Hi Rob

My Nikon did that to me once and it was a battery issue ..the mirror motor had enough voltage to get the mirror half way up and then died. I replaced with the new battery and it stayed there but by pushing the shutter button it then completed the cycle and was as good as new. Maybe Canon work the same way? change the battery and push the shutter button ... If the mirror IS stuck it's easy to see if you remove the lens!

looks to me like the shutter speed is incorrect or the upper part of the shutter isn't descending completely. If it's the mirror it's usually a spring thats broken, the shutter would be much more expensive to repair id say.