[Thumbnail cache not cleaning in v3.13.1600 (64bit)]

I was wondering if someone could help me with CCleaner not cleaning 'thumbnail cache' even though I have it ticked to. Thanks !!

[Unused file extensions?]

In 'Registry Integrity' two entries come up with the extensions .vpu and .ref as 'Unused File Extensions'. My AV Avast Home uses .vpu and Lavasoft Adaware uses .ref. Could somebody please tell me why these come up, as I have not uninstalled these programs. Is there a way I can make them not come up, as the programs are using them??

 

Any help much appreciated!!