Hi, I am currently working on a drawing but am having some issues. It was originally made on a different program of which I do not know. Each time I load the drawing a lot of the drawing is invisible. The only remedy is to set everything onto 1 layer, setting linetype to continuous and the linewidth to 0.00mm. After this the drawing works fine until I have to open it again where the lines dissapear again. This happens on both AutoCAD 2004 and 2007. Any ideas?
 
Cheers