Yup… It happened to me. I have no idea why but what I had to do is edit this file as root:
/etc/systemd/system/multi-user.target.wants/clamd.service
and replace the line:
Type=forking
with
Type=idle
and then run
systemctl disable clamd && systemctl enable clamd && systemctl restart clamd
and everything was peachy.
Cheers.
Andrzej