Regardless of which browser or computer I'm using, this happens:

When I click on New to compose a new email, I can add a contact and a subject, or even an attachment, but I cannot compose any text within the body of the email, as there is no "add a message" prompt.

When I sign out and then sign into Hotmail with my wife's account using the same computer and the same browser, everything works fine, so the problem is localized to my own account.

I have no idea what's going on, but currently I have to use my phone to send emails, since my Outlook.com account is inoperable. 

Does anyone have any ideas?  Thanks!