What do I have to do with this error - where to change anything? If I would like to change the profile data only the error message will be displayed....
...this user isn't able to change his profile data - he always gets directed to the dashboard with this error message.
I solved the problem with a login via Facebook and afterwards disconnecting the profile....now it's working fine again. It seems that once connected to Facebook you cannot edit your profile when using the "normal" login...?