I installed Avast and it seems to be running, although my Windows Security Alerts says that the software definition is out of date. When I update, Avast says it is up to date.
I would first suggest that you check the system date, especially the day, month, year.
If this is correct then try a repair of avast. Add Remove programs, select ‘avast! Anti-Virus,’ click the Change/Remove button and scroll down to Repair, click next and follow. You need to be on-line to do this. This has on occasion synchronised the apparent difference in VPS version update date reported and what it actually is.