AYahoo (business) mail account with two email addresses stopped working correctly on Firefox a few days ago. Ok in other browsers, ok Firefox on other comuters.

Was working just fine until a few days ago. We have a Yahoo business account, with two email addresses. Normally we can only see one email account at a time, and to change the views, there is a dropdown box upper left of Yahoo mail which normally allows selection of desired account. Now within the last several days, selecting the dropdown box only takes us to the Yahoo Profile update page, not the dropdown menu which lets us change the email account we want to view. Correct operation is noted in IE9, but neither Firefox 32bit or 64 bit allows selecting the second email address.