Megan; I agree, you have a circular reference created when you open those two schedules in the master project. The problem is finding it, which isn’t easy. Might I suggest the following approach. 1) Open one of the two schedules and remove ALL external links, documenting each as you remove them. Then, open both schedules. If the circular reference still appears, none of the links you removed caused it and they can be re-added. Do the same process with the other schedule, removing all external links, documenting them, and re-opening. When you can open both schedules with no reference errors, you know one of the removed links caused the issue. 2) Add the removed links back one at a time. When you add a link and the message reappears, you’ve found the culprit. 3) Follow the dependency chain to see and analyze the full circular reference. Hopefully, once you see the full circular reference chain, you’ll be able to determine how to fix it. The problem could be the task you are adding the external reference to itself, or it might actually be one of the tasks somewhere in the circular reference chain.