my.yahoo.com behaves incorrectly on LTE, but it is OK on Wi-Fi

I have an iPhone 5/ATT.

When I visit my.yahoo.com using my LTE connection, this is what I get:

It knows who I am. It says, "Hi, Roberto", but then it is asking me to "re-enter my password".

I enter the correct password, and it comes back to this screen. It is asking me to "re-enter my password".

Never ending. Observe that I am connected via LTE.

So, I connect to Wi-Fi, and try again. Voilá. It works. See below:

It did not ask for password. And it is showing my Finance Portfolios correctly.

So, my reaction was that Safari was screwing up the pooch.

I downloaded the Chrome browser from the app store and repeated the same steps.

It behaved just like Safari did. Can't blame Safari then.

Could it be IOS 6 that is screwing up?

Or is it Yahoo?

Can someone help? I need to look at my Portfolios when I am away from Wi-Fi.

On a separate note: I have seen many posts about problems with Yahoo mail. Could it be the same LTE vs Wi-Fi thing? Will someone try it?

Thanks,

Roberto