I'm guessing you have created a master project ! If so, you will need to
check all the cross project task dependancies to hunt for a circular
reference. By no means a small tasks if the plans are large.
If you have a number of child projects, you could try recreating the master
with one child project at a time so as to ascertain which child project
contains the circular reference.
In addition to Paul's sage advice, I would recommend that you also check for
dependencies set on summary tasks. We recommend that you NEVER set
dependencies on summary tasks, as that is one of the primary sources of
circular reference errors in one or multiple projects. Hope this helps.
