I just did it. So here is how it works for me: launch the CK in on line mode, launch the Windows task manager, locate the Steam.exe *32 process, right click on it and kill it, unplug your computer from the internet, launch Steam and choose the off line mode, launch the CK again; this time it will start, re plug your computer to the internet, if you need it. Launching two instances of the CK 64 bits requires that the line bAllowMultipleEditor