After installing Kapersky Antivirus from fresh and trying to activate the product with a Key file , it came up with the following error “Activation error. Digital signature is either missing or corrupted” I redownloaded the key file and it still brought up the message. After looking on Kav Knowledge base , and looking to check if the Ask toolbar was installed (which it wasn’t). I unistalled Kapersky , Restarted the Computer and rinstalled. This resolved the problem!