Autocad Conflict between data table in open drawings.

I just launched a drawing of a specific project in AutoCAD but the error below keeps showing up.

The error message is stating that there is a "Conflict between the data table in open drawings".

Message details

. Parameter. ERRCODE: Value: 786433

.. Parameter. ERRCODE: Value: 786433

.Error: 786433 . Conflict between data tables in open drawing.

.. Error: 786433 . Conflict between data tables in open drawing.

. Parameter. APPLNAME Value: ad

.. Parameter. APPLNAME Value: ad

. Parameter. CLASSNAME Value: pip

.. Parameter. CLASSNAME Value: pip

I don't know how to fix this and what is causing the conflict between the data table on my drawing. Please help me on this. Thanks.