I realize this is a few months old, but I had a problem with CCleaner and Avast!
It may or may not affect anyone else, so I'll give the short and long version:
Short:
Avast! wasn't cleaning up the unp temp files from \windows\temp\_avast5_. I changed CCleaner options and Avast! started working. Changed the options back and... Avast! was still working...
A bit longer:
The folder was 6 GB when I discovered it and cleaned them out. Was able to select all except the webshlock.txt file, which is how it should be. If anyone doesn't already know, Avast! uses this folder (\windows\temp\_avast#_ where # is the version of avast, has done it since at least avast4) to drop a file, scan it, then delete it. Well, mine were not being deleted. The usual cause for this is another program having 'hooks' in it so Avast! can't delete, and it's generally some resident security software that ends up being the culprit.
Although CCleaner isn't 'security' software, per se, it has a checkbox option in it, "Only delete files in Windows Temp folders older than 24 hours," so I unchecked that. I also added the _avast5_ folder to the exclude list. Voila, Avast! started deleting the files! And then the mystery... to figure out which of those two options had caused it, I put the checkmark back in the box. Still deleting files... ok, remove the folder from exceptions. um... still deleting files. Ok, so I don't know what's going on.
I had a rootkit virus walk right past Avast! about two months ago. Ended up using MBAM, combofix, and 3 or 4 other utilities (plus manual cleanup of .exe files) to clean it (it was nasty. virus and trojan packed with malware/adware to distract you while the virus worked), got everything finally working again, reinstalled Avast! and installed CCleaner (not sure which order I installed them, but dates seem to point to Avast! being reinstalled after CCleaner). The point of this long-winded rambling is that it could be something entirely specific to my machine alone and will never happen to anyone else ever, or it could be a problem people are having and they don't realize it because they use the windows utilities to clean their temp files or some other utility, so they never realize it's happening. The only reason it affects me is because of how I have my partitions, my windows drive is only 20GB. So yeah, 6GB of pure garbage files is painful to me.
