Issue with the display of Proxy elements that are generated by AutoDesk Mechanical 2000.
If the file was created in AutoDesk's Add-on package, Mechanical 2000 standard AutoCad will not even allow for editing without this add-on package. AutoCad will display the element "like MicroStation" with a boundary box around the elements. If this file needs to be used by straight AutoCad the file should be Exported from Mechanical 2000 to a plan AutoCad format. This will remove the Proxy data from the file & replace them with "normal" AutoCad elements.
If the file needs to be manipulated in MicroStation the element should be selected & Unlocked by going to Edit> Unlock. Then select the element again & then Drop the Cell data to regular elements.