Zend certified PHP/Magento developer

Error when adding a user

When I try to create a user, I get this error:

“Rolled back transaction has not been completed correctly.”

In system log I get:
main.INFO: Broken reference: the ‘notification.messages’ tries to reorder itself towards ‘user’, but their parents are different: ‘header.inner.right’ and ‘header’ respectively.

Any idea?