I am shooting from the hip here but if I remember right I had the same problem, I know the hub has to be registered separate from the other Samsung services since it has paid content and needs some sort of payment system (credit card, whatever) linked to the account, you can use the same account but must set it up in the hub settings.
I am guessing you lost part or all of this info in the update, did you try to reset up just the hub?
It's been some time so maybe I am all wet but it would be an easy try to see if it fixes the error. (though if you want the update you might update again first instead of having to set it up twice (if this even works, fingers crossed).
Double Checking, Looked elsewhere....
Yea, Sounds like it's worth a shot.
"The Music hub needs an own account. It doesn't use your google details to log in.
Go to "My account" or whatever it's named when the music hub is open (The tab at the far right.) and register. "