I have been dealing with this "Modeler Dll - Fatal error" for most of this year now. I have run full version AutoCAD & Inventor for the past 4 years, this year I decided to only go with 2008 Lite. I get the error immediately upon opening my existing drawings. I have repaired, reinstalled, uninstalled all Autodesk products, reinstalled, everything but reformatting my system.
I had troubleshot one of my drawings and found a single Block that was creating the error upon opening the file, and was able to eventually open it in Lite after editting the Block. I get the error now while in the drawing and moving the crosshair over certain lines/blocks.
On another note, a coworker who had never installed AutoCAD on their system before, installed 2008 Lite and can open all the drawings with no problems. It gets to the "Loading Modeler Dll's" script while opening the file and cruises right on by it. Does not get the Fatal error at all.
This all has led me to believe it is a registry or system dll glitch from having previous AutoDesk products on my system and reverting to 2008 Lite.