This article is a legacy article. It applies to previous versions of the Liferay product. While the article is no longer maintained, the information may still be applicable.
If you have a user that has a friendly URL page like "myca" and that user tries to join the user group that also adds another friendly URL "myca" there will be a batch update error. This occurs because two pages can not have the same friendly URL.
The error occurs when the user group's pages are added to the user. If the friendly URL already exists, it will not allow you to bring that user into the user group and you will receive a batch update error.
To resolve, simply delete either the user group's friendly url page (within the manage pages section) or delete the user group's friendly url page. Obviously, it would be much easier to delete the user group's friendly URL page rather than changing pages for each individual user, but the solution will depend upon the needs of the environment.