I'm also receiving this same error message. Was able to log in successfully one time with main character "Fitzwilliams" on AB... logged off to character select, picked another toon "Venklor" and clicked "Play".... I got this same error message about character not being found - repatch.
I exited and re-launched EQ - only saw 4 characters in the pick list, attempted to re-log in again and received "Unable to find your character" message.