I have a user that used Plant 3D 2013 to create a plant drawing. He is trying to annotate it with rev triangles, section lines, etc. that are just normal vanilla AutoCAD objects. When he tries to insert them he gets this error dialog:
This application has detected a mixed version of AEC objects participaing in this operation. Newer AEC objects will be disallowed from participating in this operation.
The objects should not have AEC objects in them. I even ran the function AECTOACAD on a rev triangle to remove any that might be hidden and then tried to insert it with no luck.
More info - The problem seems isolated to one drawing. This drawing has an xref and components that are from another department. This department has been known to use converted Solidworks drawing elements in their models. I don't know if that is signifigant or not.
I'm pretty sure base AutoCAD has been including some types of AEC objects since 2008. Maybe the problems are more of a sign that some objects haven't been converted correctly.
I'd start looking at the file versions and see if there is some sort of mix between 2007, 2010, and or 2013.