I get warnings about "Attribute type -1 not recognized"

CGM has a "geometry attributes" capability which allows applications to define their own attributes, and write those attributes to the geometric model when the model is saved to a file. Attribute types are registered with the attribute manager upon instantiation of CGM, and are assigned an ID number. When reading in a new model, CGM matches the attribute name to a previously-registered attribute name and returns the ID number. If an attribute is found whose name has not been registered, CGM emits the error:

ERROR: Attribute type -1 not recognized.

CUBIT uses attributes to store mesh-related data, including things like mesh scheme and mesh interval specified by the user. When a model from CUBIT is read into CGM, the CUBIT attributes will not have been registered, therefore you get an error when those attributes are encountered.

More information about CGM's internals can be found here and here.