I also ran into "Error Opening file for writing" for the ccleaner64.exe file. The solution for me was to have the folder for the CCleaner files open and at that point change the extension to .old and then click on the Retry button. The update proceeded until hitting the branding.dll file. So, I did the same thing: changed the extension for that file to .old and clicked on Retry. The update then completed the task and I was updated to version 5.55.7108.