Did you choose the custom or non express setup for the CCC installation, as I believe it should prompt for single/multi user install, and if that doesn't fix it - try a right click on the app icon and choose 'RunAs' to run it as admin if available - and if for whatever reason your system is using any extra protection from casual changes, then you'll need to enable changes for your log in as well - simply guarding against system hijacks I guess?
As OS's above XP will normally check to make sure you are the admin before running a potentially system changing enabled application.