I keep having a problem with sign-in on Windows Live Mail. I try to sign-in using my default email address. No good !  I'm prompted to try again using a different address. So, I use my Hotmail address and 'POW'... I'm in. I receive my default mail through this sign-in method, but not my Hotmail. What is happening here ?

Oh, yeah ! My security keeps sending me a message saying the Windows Mail certificate  is invalid and gives me a choice of 'Disconnect' or 'Move on' at my own risk. Why would Windows Live Mail be using an invalid certificate (virus?) ?