I did some testing and CCleaner also removes all stored data from a full scan. The first time I ran CCleaner on avast!, it cleaned 18MG's of something, and each time after that, it only cleaned a few KB. Today, I used CCleaner to clean everything, including avast!, then I did a manual full scan, and it took 8min longer then normal (29 vs 21). Then after avast! finished I analyzed with CCleaner, and what do you know, there was 18MG's again waiting to be cleaned...............I have unchecked the avast! box, and will not clean it again. It defeats the whole purpose of avast! storing files in the persistent cache.