HELP!!! Avast can't update

Avast Free Antivirus / Premium Security
1

Avast can’t update its virus definition. It indicates: Invalid file signature. Setup will terminate. I tried repair and reinstall, but both of them didn’t work. Is there any one knowing how to solve it??

2
  • Which avast!..?? (Free/Pro/IS)
  • Which version…??
  • OS…?? (32/64 Bit…? - which SP…?)
  • Other security related software installed…??