Probably the shape CIRC1 does not exist.
If someone has changed the linetype in the LIN file and added a new shape to the SHX File, both files has to be distributed. Linetypes get saved inside the drawing once they are loaded, but shapes are not.
It is better to not add shapes to a default AutoCAD SHX file, instead create a new SHX file. If you miss that file, you only get the message that the SHX could not be found, but no linetype errors.