The Avast antivirus service had not started.
Patrick, can you see into Windows Events if there is any error related to services not starting...
It's strange that avast service does not start

How are set your avast! services? Control Panel > Administrative Tools > Services
I suppose you have to have four avast! services:
C:\Program Files\Alwil Software\Avast4\ashServ.exe (avast! antivirus service)
C:\Program Files\Alwil Software\Avast4\ashUpdSv.exe (avast! Update Service)
C:\Program Files\Alwil Software\Avast4\ashWebSv.exe (avast! Web Scanner service)
C:\Program Files\Alwil Software\Avast4\ashMaiSv.exe (avast! e-Mail Scanner service)
The two first of them should be Automatic loaded and the two last Manually loaded.