Save failed with the following error: Duplicate entry '0' for key 'PRIMARY'

Hi,

I have a new site under production using J3.2.0 and subsequently upgraded to the current J3.2.3. Components include latest versions of Jomsocial, EasyDiscuss and EasyBlog. Earlier we had installed Kunena but uninstalled it when we decided on EasyDiscuss.

Today, I created a new user via the backend and got this error:

Error
Save failed with the following error: Duplicate entry '0' for key 'PRIMARY' SQL=INSERT INTO `mcq13_discuss_users` (`nickname`,`description`,`url`,`params`,`points`,`location`,`signature`) VALUES ('','','','{\"facebook\":\"\",\"twitter\":\"\",\"linkedin\":\"\",\"skype\":\"\"}','0','','')


How do I solve this?

Thanks