Outlook keeps asking for username and password (SBS2008)

This seemed quite a common issue a little while ago and I'm sure a Windows Update caused the problem. It is very annoying for users, as they are bombarded with logon credential boxes while trying to use Outlook. Even though they put in the correct credentials, the box keeps requesting them.
Fortunately it's a quick one to fix:

Go to IIS Manager -> Sites -> SBS Web Applications
Select Autodiscover
Open SSL Settings
Under Client Certificates select Accept
Click Apply

Restart the World Wide Web Publishing Service

If this does not resolve the problem, do the same process for the following:

• OAB
• owa
• Rpc
• RpcWithCert

With this fixed, the users can go back to happily sending out chain letters or whatever it is end-users do these days :-/