Here's another reputed antivirus which should be in your blacklist: Webroot Anti-virus.
A lot of Windows 8 users have complained that they can't sign into Windows 8 with a Microsoft account and the only error they're seeing is an incorrect password message.
"We have identified a problem where some users can't sign into Windows 8 with a Microsoft account," a forum moderator on Microsoft's Answers forum explained.
Webroot anti-virus software prior to version 8.0.2.79 removes some core Windows 8 registry entries, so the operating system blocks users from signing in with a Microsoft account. This particular version, however, resolves the issue, so all users are recommended to update as soon as possible.
"If you only sign into your computer with Microsoft accounts, and they all return the 'password is incorrect' error, you will need to reset or restore your computer to a point prior to Webroot being installed in order to sign in to update Webroot."
Source: Microsoft, Softpedia