Strange situation with SeaMonkey & new Yahoo

As it is right now, I have no problem accessing Classic Yahoo with Google Chrome,SeaMonkey or Firefox. Yet I try accessing New Yahoo beta with SeaMonkey & it will NOT do such. It simply states ;

Your web browser doesn’t support Yahoo! Mail Beta

Download the latest version of a supported browser for free:

* Firefox
* Internet Explorer (for Windows)
* Safari

Do I need to wait till its out of beta,or ??? TIA

The new Yahoo email has poor browser support and also other problems. In fact, many users aren’t happy with it for a variety of reasons, see e.g. this thread:
http://www.techspot.com/vb/topic165392.html

This provides further proof that new is not necessarily better, while betas have always been known as something to avoid. Of course, nobody can tell you how things would be out of beta, not even Yahoo itself. All I could advise you is:

1 Report the problem to Yahoo
2 Stick with the old version till you’re forced to change
3 Just to be on the safe side, since Yahoo don’t seem to be at their best, create a new account, e.g. with Gmail, so that you’ll be independent and prepared for the worst.

Thank you for your reply & yes,I'm aware of beta. Its my understanding the up grade is NOT mandatory,but prefered.
I already have accounts at Gmail & I will report it to Yahoo.
Again, thanks for your input & have a great day.