There is a shared cell in this library. Unable to remove it.
This cell was attached as a library Shared cell.As of MicroStation 8.1, shared cell definitions (or blocks) can be placed from the active cell library using the normal Cell Library dialog (elements > cells). The attached file can be either a DGN or a DWG. These cells are designated with the letters LbSh (for Library Shared) in the Where column of the Cell Library dialog. By default this capability is enabled; however, it can be disabled by turning off the CAPABILITY_SHAREDCELLS_FROM_ATTACHED_LIB capability .