There can be a number of reasons. Are you able to do "import dxfLibrary" from the python console without errors?...

Commenting post 139: There can be a number of reasons. Are you able to do "import dxfLibrary" from the python console without errors? As a sidenote, it's best to use the FreeCAD forum at http://forum.freecadweb.org for that kind of stuff... More people will be able to help.