Hey Cole,
I didn't find any bug or article related to changing the common name in WF 3.0. However, in TPI #124152 (titled "The Use of Common Name when Creating a New Object in Wildfire 2.0"), there is a statement:
"For Wildfire 2.0 Common Name is used for data management only. For Wildfire 3.0 (or beyond), it is planned that the "Common Name" will have more applicability in the Pro/ENGINEER User Interface."
I don't know if this means you can no longer change the common name (easily at least) through the parameters, the common name may have become ingrained permanately with the part upon creatation. This might be the reason is claims it is reserved when you change it, it may be created but not allowed to be changed. You cannot even create this parameter if you use the "Empty" template.
I am not expert on this, its just an assumption.