A name change is required to log in.

[EnriSol]

Did you right click on your character name and access the name change via the sub menu that pops up? Is that where the error occurs as well?

Yes, but I get the same text box, a name change is required to log in with this character.

[Freyar]

Just have to keep trying until it permits it. I think if you see your character data, you end up with that request going through.