Repair Avast:
1. Avast GUI -> Settings -> Troubleshooting
2. Click on 'REPAIR APP'.
3. Follow instructions.
4. Reboot.
I kind of wonder though why updates keep breaking smart scan. In a short time this is the second time the smart scan broke, first time they fixed it with a patch.
Makes me question reliability to a degree. This install of Windows is only been 3 weeks with avast on it, so I doubt there is something wrong with the pc itself, seeing I didn't install nor browse that much.