Same problem here on Windows 10 x64 Pro 1909 - installed 5.64 update, and when I run it, the CCleaner window is completely frozen and doesn't respond to anything. Can't be closed by right-clicking on the app icon in the system tray and selecting "Close window". Has to be killed via "End task" in Task Manager. I download the update a 2nd time from https://www.ccleaner.com/ccleaner/builds, but a binary compare of that with the original download from Filehippo shows that the two are identical. Uninstalled 5.64, re-installed 5.63, and it runs fine. In Event Viewer there are multiple events from Windows Error Reporting in the Application log showing:
Fault bucket , type 0
Event Name: AppHangB1
Response: Not available
Cab Id: 0
Problem signature:
P1: CCleaner64.exe
P2: 5.64.0.7613