What avast version free/pro/AIS/Premier and build number (latest is 2016 11.1.2241) ?
Try an avast Repair:
Control Panel - Add Remove Programs - Avast antivirus - Change - from the next window select Repair.
OK your way out, Reboot.
Have (or did) you another Anti-Virus installed in this system, if so what was it and how did you get rid of it ?