Circular Relationship error When indenting task
In Microsoft Project, if two tasks are linked in a predecessor/successor relationship and you indent the successor to make it a subtask and the predecessor of a summary task, you may receive the following error message:
This outline change would create a circular relationship. Indenting these tasks would create an illogical relationship with other tasks. Check the task dependencies for the tasks from which you are indenting, and then try again.
This problem occurs when the predecessor task has a cross-project link as a predecessor and the task you are trying to subordinate is its successor. For example, let's say you have two tasks (A and B). They are linked by a Finish to Start relationship and Task A has a cross-project link to a task in another project. If you indent task B under Task A, you will receive this error message.
To work around this problem, remove the predecessor and successor link between the tasks and then indent the task.