Yesterday
From what I been able to gather, Avast destroyed 14 files by claiming they all contained the same Win32:Tenga virus. I reran MBAM and there is no difference between what was mentioned previously and now. Ran Spybot and besides a couple questionable cookies, Spybot encountered nothing of elevated concern.
I again manually restored all 14 files from backup. Then did a comparison by using the old individual PAR2 check files in the original directories and they are all identical.
In the case of Firefox, I went a step further and re-downloaded the installer. The installer passes the old PAR2 check file, a quick binary comparison and a SHA-512 comparison with the original Firefox installer. For all measurable purposes, the Firefox installer is identical! Yet, Avast wants to destroy the file as soon as the file is copied back to the original location.
After the first round of destruction, I set the maximum size of the Chest to zero (unlimited) and the maximum size of file to 2,097,152 KB (2GB) in an attempt to avoid a file from getting destroyed when it's placed into the Chest. As I mentioned before, this didn't make one bit of difference since these 14 files still got destroyed even though I tried my best when the threat dialog appeared to tell Avast to do nothing.
Sadly, at this point there is no direct selectable option to do nothing in Avast. The only option is the close gadget in the left corner of the threat dialog. Unfortunately, this arrogantly suggests that there would never be a time that you would want to do nothing. And yet, I watched in total amazement while Avast destroyed 14 files with each click of the close button on the thread dialog.
In any case, it's interesting to note that some of these files are the exact same ones that were destroyed previously. These include such installers as the Firefox browser, Microsoft's DirectX, Microsoft's Intellipoint Software, Synaptics TouchPad driver, two WinAMP installers and two WinAMP plug-ins. All originally downloaded from their respective websites.
Based on the above, this suggests to me that while this is not likely to be a widespread issue, more likely a specific issue, Avast does has a repeatable Virus Chest bug. Of course, none of this would be happening if not for the Tenga false positives.
Today
Speaking of which, Yesterday evening I disabled the File System Shield until next reboot. A few minutes ago and without rebooting the computer, I re-enabled the File System Shield. I then did a manual scan of the same Firefox installer. No threat was detected.
I see that a new 110514-1 brain file was downloaded while I was away. It appears that this new brain file might have included a new Tenga definition. Either that, or disabling and enabling the File System Shield is related to the issue.
It would seem to me that regardless of the state of the File System Shield, which would likely only trigger the event, the fact remains that there is a Virus Chest file destroying bug within Avast.
Please, does anyone have any further suggestions to help Avast, and ultimately all of us -- diagnose and find this bug?