pwillener, on Dec 10 2007, 03:07 AM, said:
How are you doing the update? Download and run the installer? Make sure CC is not running when doing the upgrade install.
...along with those recommendations it can sometimes be because of a corrupted download in your web browser Temporary Internet Files ("Cache"), and when re-downloading the file it's just getting it from what's already been downloaded in the browser cache. In some instances it may be necessary to empty your browser cache files before downloading the file again.
Other than that, it may also be necessary to restart Windows, and then install CCleaner. Or do a clean install of CCleaner (uninstall the old version, then install the new version) has worked for other people that have mentioned an issue about not being able to install a newer version.