Plotting problem using SMI Plot 4.0?

[lewcox]

I'm trying to work back and forth with a fellow land surveyor who uses SMI Plot 4.0, I use Autocad R12. I sent him a dwg file which he imported into his SMI Plot 4.0 drafting program. He did a lot of editing and additions to the drawing file. When he went to test plot the drawing file using his SMI Plot 4.0 program, all the plot would produce was one line weight. He used several different colors to define different line weights just as he has done may times and it only produced one line weight for all the many entities. I got this dwg file from a company that digitized topo contours into it for me, then I forwarded it to the SMI Plot 4.0 user. Other dwg files I have sent him in the past have worked fine and produced the different line weights, but this dwg file which he imported in the same way as previous dwg files doesn't produce the various line weights when plotted. Does anyone have any idea what might be going on here. Could this be a setting problem with his SMI Plot 4.0 software. Any help or ideas will be greatly appreciated.