vango:
From the MEP Modeler User Guide (p55):
If a project created in an MEP environment is reopened using ArchiCAD
only (without MEP Modeler), the MEP objects are available, although
locked for editing. If you wish to edit or move these elements, you must
first unlock them individually (Edit > Locking > Unlock). Their MEP
connection information - once you have edited them in a non-MEP
Modeler environment - is lost, and they behave as plain GDL objects in
ArchiCAD.
David