Whenever I open Windows Live Mail on my laptop (Win 7) I get a message saying "the email address or password is incorrect. Please try again"

It's NOT incorrect. I can log in on the web no problem so it's not a wrong password or mis-spelling. I can also access it fine through my ipad and iphone so It must be a problem with Windows Live Mail.

This is really driving me to distraction. Can someone please help?