I’ve been hit by Avast not running too. Here are a couple of observations that might point the way to Avast fixing the problem.
On the Avast web site my computer shows twice on the list of devices. The first indicates OFF and last communication back in December, when I last renewed. The second indicates SECURED with last communication 5 hours ago (it is now 13:00Z) from when I used the PC earlier this morning.
The avast! Antivirus service has started but the buttons in Services (Start, Stop, etc.) are all greyed out. That tallies with no effect from clicking Turn On Now from Windows Security Center and Fix Now and Start Program in Avast.
As others have reported, my current registration is due to expire 17/12/2013 but I have 0 days remaining.