When you rename the installer (to CCleaner.exe in this case), the setup locks somewhere at the start.

Hope this will be fixed in feature releases.

The reason that exists is so that if you already have CCleaner installed and attempt to install a new version, it will force close the running CCleaner application in order to overwrite the old one with the new one.

Simply leave the install name as it is, or name it CCleaner123.exe (or let the numbers be whatever the version is).