If you’re a developer: never hook into acadres.dll directly—use Autodesk’s documented ARX/DBX APIs instead. For end users: keep your backup of acadres.dll from a known-good installation.

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\App Paths\acad.exe HKEY_CURRENT_USER\Software\Autodesk\AutoCAD\RXX.X\ACAD-XXXX:XXX\Profiles Ensure the Path string points correctly to acadres.dll 's folder. Also, look for any AppInit_DLLs under: