Selecting print area of a drafting, ability to print out a drawing in parts

I have installed and registered ProgeCAD LT 2005. When I try to open dwg-files,
a thick white line shows for a moment, than there is a black screen. When closing
this file the question about filing shows up. I know that these dwg-files were
converted from another CAD-software than AutoCAD. Other files work properly.
Any suggestions?