A few users on our site gets an error when joining a club. Most of the users doesn't get this error. The error is:
Message: Sys.WebForms.PageRequestManagerServerErrorException: Could not add membership for user with id 8293 to club with id 2.
The user gets added to the club anyway. But the user is not listed in the list of group members in edit-view.
The problem was the events in SecurityModule.cs. It crashed because a the role for a group didn't exist in the RoleProvider.