This sounds very familiar CADaver
http://www.theswamp.org/index.php?topic=17389.0
Although I found a few other cases on the AutoDesk forums I couldn't find any solution, sadly a complete re-install of AutoCAD failed to fix the issue either. I'll be wathing this thread with interest.
That one is still different from this, none of your lisp worked. Here EVERYTHING works just fine except anything with VLA or VLAX functions. We're re-installing a whole new image this morning, I'll keep you posted.
