Mail 8.2 doesn't work anymore

For some reason when I open Mail, I don't even have a window that shows my inbox. I've tried everything including trying to open a new viewer window, and various preferences. All I have is a blank screen....crickets. Nothing. I tried to install a mail update, and it says that my disc won't accept this update. Argh....

Anyone have any idea what went wrong, and how I can bring my inbox window back?

Thank you in advance for any help.

Bianca