Corrupted Archive file, this could simply mean that avast is unable to unpack it to scan the contents of the archive and assuming it is because it is corrupt.
Even if it were corrupt there is nothing that a user can do to resolve any corruption, short of replacing the file. This I wouldn't recommend (especially if this is for archives in the \System Volume Information folder, part of the system restore function) unless you are getting problems relating to that file outside of the avast scan.
