These errors occur due to an infinite loop in a workflow. An infinite loop occurs when one operation triggers another operation, and then the second operation triggers the first again.
For example, a workflow uses a Set Field Value action on an After Field Edit trigger and the Client Field property in the action definition equal to a specific field on the record. If a user edits the field set for the Client Field property, an infinite loop results as the action is continually executed.
An example of an infinite loop in a workflow is a workflow for a purchase order record. The Employee field on a purchase order is dependent on Vendor record, and the list is restricted to employees that belong to the vendor subsidiary. Consequently, the Employee field reloads when a vendor is selected. To avoid this type of infinite loop, set the Employee != Current User condition as a workflow condition.