I am still having this problem.
I also have this problem when I use Corel 10 or export to .eps.

I finally export this to .DXF, import it into Corel x3 and then it exports well to PLT,

Does anybody have an idea what is wrong??

Do I have a wrong setting?

Thanks for all your help.

I just solved the problem

I went to the outline tool and made the line thicker. It now exports beautifully