I ran into the exact same problem, just this morning. I have Win 7 (64bit), popped in the Civil 3D 2010 disk, and installed the CMCU. Got the same error. So, it seems the CMCU on the 2010 disk is for 32bit only.
Where I work we have various Autodesk products, I grabbed AutoCAD Architecture box, which includes a specific 64bit version install disk. Popped it in, installed the CMCU tool from it, and the application works.
So . . . See if you can acquire a 64bit CD install. Don’t know if the download will include the tools.
Autodesk should simply post all their add-on utilities in a library (subscription) for us to use. So much tucked away in odd places. Anyway, don’t want to rant on. J Good Luck.