Hotmail users are getting an unusual error when trying to sign-in to the service. Even for the correct credentials, the webmail service is returning a “401 – Unauthorized: Access is denied due to invalid credentials” error when signing in. The problem has been reported by many users over at Microsoft Community forums. Apparently, users are able to sign-in from their mobile devices but when using a PC/Laptop, the error shows up. “401 – Unauthorized: Access is denied…