Hi there,I received an external architects drawing and when i look at it, some of the lines appear missing, however when i pan around the drawing they magically reappear only to become hidden again when i stop panning.Does anyone have an idea if there's something set wrong on my Autocad that is not allowing me to view these lines? I'm using LT 2012 by the way.Thank you.

Have you run PURGE, AUDIT?

It could have something to do with the program the architect used to create the drawing in the first place.  Call and ask him if it was one of the AutoCAD vertical products (i.e. - not plain AutoCAD).