Well my quest is that is a remnant of Symantec/Norton (or you still have it installed ?) and that is supposed to be its quarantine (not very good if avast can scan within it) and avast is detecting old detections sent to quarantine, but because of limited protection is unable to move them to the chest.
You don't say why avast can't move it to the chest, but I suspect it is error 00000005 (5) access is denied.
Have (or did) you another Anti-Virus installed in this system, if so what was it and how did you get rid of it ?