New Yahoo Mail Not Working?

After switching to New Yahoo Mail (version??), within 2 days I could not attach any files to new email and now cannot open the 'Inbox'. Login appears to function OK, but when I click on the Inbox, its completely blank (rest of page around the margins is unchanged). Most of the action buttons are non-functional, although 'Signout' still seems to work. I want to return to the previous version of email so that I have some vital functionality. Maybe this is my lesson for depending on a free email service (you get what you pay for?). Other, but seemingly unrelated info is that I upgraded Firefox (to ver 5) at about the same time, but this problem is the same if accessing from IE9. Any help appreciated.