I recently tried buying an app from the Nokia store. When trying to pay with Visa, I got continuous error messages, so I thought 'let's delete the Nokia account from this phone and start all over'.
Which is what I did, and now I can't sign in to my Nokia account at all anymore (not through the Store app, not through the Accounts list on the phone).

Same happens for Dropbox. I have an account, but can't login on my N9.
The error message I get is either 'Account won't save' or 'Unknown error. Try again later'.
I have tried connecting via several networks (wifi/3G), and have also done a soft reset.

Does anyone have an idea how to solve this? (I'm kind of reluctant to try a hard reset)