Some further information:
When the Google Drive application is running, it creates a directory under C:\Users\Chukhung\AppData\Local\Temp with a name like "_MEI54082" (the last five digits of the directory name change every time the Google Drive application is started). Within this directory are a large number of subdirectories, DLLs, and what appear to be Python files. This directory disappears when the Google Drive application is shut down manually.
I looked at the contents of this directory before and after running CCleaner (while I left the Google Drive application running).
The _MEIxxxxx directory went from 24.2 MB, 170 files, and 93 folders to 18.5 MB, 33 files, and 0 folders after I ran CCleaner.
I'm guessing that Google Drive gets seriously confused when CCleaner partially deletes the contents of this directory.