Avast gives you the reason why it can't be scanned, what was that reason ?
I suspect that this was archive was password protected ?
Files that can't be scanned are just that, not an indication they are suspicious/infected, just unable to be scanned.
Many programs (usually security based ones) password protect their files for legitimate reasons, there are others (and avast doesn't know the password or have any way of using it even if it did know it). Some program updates alsp protect their files, adobe flash player being, one and possibly related to this file.
By examining 1) the reason given by avast! for not being able to scan the files, 2) the location of the files, you can get an idea of what program they relate to. You may need to expand the column headings to see all the text.
If you can give some examples of those file names, the full locations and reason given why it can't be scanned might help us further ?
Essentially you don't want to delete or rename something just because it can't be scanned.