Avast! Free AV 8.0.1489 on W7u x64 often reports as not running

Subj: Avast! Free AV 8.0.1489 on W7u x64 often reports as not running.
The system alert in the tray and recommend to switch it on manually … but it does not happens when I do it!

Any suggestions?

Thanks in advance.

Repair avast!:

  1. Control Panel → Add/Remove programs → avast!
  2. Click on ‘Repair’.
  3. Follow instructions.
  4. Reboot.