I've also re-downloaded the client, ran as administrator and unchecked the read-only option on the game folder.
Edit: Jump to the thread for a fix that worked for me. This fix was recommended by an official developer here at RoR.Genisaurus:
try changing your password again to something all lowercase. No numbers, no "special characters," just the 26 characters in the English latin alphabet.
Edit: I've put together this Google Document of the English alphabet for those that may need it.