AutoCAD 2008 linewight plotting issues

I have recently been working on a set of drawing for school using Autodesk AutoCAD 2008 Educational Version. I have had this program on my computer for about two years now and have never had any issues with it. When I work on drawings, I always divide different elements into layers and then assign lineweights to the entire layer. Recently, different lines on the same layer with the same assigned lineweights have been plotting drastically different widths. I have made sure that Lineweight Control is set ByLayer and that I have not mistakenly assigned a unique weight to a single line.

In an effort to correct this, I have even gone back to certain drawings and manually assigned lineweights to each individual line, but they still plot at drastically different widths. As an example, I have a simple 2D box drawn from 4 lines. Although all of the lines are on the same layer and set to plot at 13 mm, only two of the lines will print at 13 mm and the other two will be at least twice that width. I’ve checked and rechecked everything I’m aware of that affects lineweights, but nothing is working. I always plot to PDF to review layout before printing a hard copy, if that makes a difference.

Since I’ve never had this problem before, I assume that I inadvertently changed something, but I’m just not sure. Any help would be greatly appreciated.

Possible driver problem? Make any changes recently?

Not that I am aware of. The problem has only been happening recently. It seems to be completely random which lines print as intended and which ones plot too thick.

Try running an AUDIT on the drawing then plotting it out. Any change?