I have one the same problem with the latest update.

*Avast reports that it's in passive mode, I turn passive mode off, Avast offers restart. After restart Passive mode is on. I cannot turn it off.
*Avast reports that anti-rootkit monitor if off. Clicking enable does nothing and under Troubleshooting options Enable rootkit scan at startup and enable rootkit monitor remain checked.
And every time I start my OS, Avast must restart the system ...

I have no other antivirus installed on my system and that microsoft security essential was uninstalled completely 2 years ago.
I have Windows 7 64 bit and Avast program version 17.7.2314 (build 17.7.3660.0).
EDIT: Can not also disable the antivirus. (10 minutes, 1 hour, ...).