I have built a reactor that when the dimscale or tilemode is changed: it calls the following function to regen the drawing (so that the changes are visually reflected) (defun al-Regen () (vl-load-com) (setq thisdrawing (vla-get-activedocument (vlax-get-acad-object) ) ) (vla-Regen thisdrawing acAllViewports) (princ) ) Works fine in AutoCAD 2005, In AutoCAD 2004, when I toggle to tilemode = 0 I get the following error message: ; error: Exception occurred: 0xC0000005 (Access Violation) ; warning: unwind skipped on unknown exception Any ideas on why? All help appreciated.