How do you open an arf file? Something happened to my drawing, and I got an internal diagnostics fault 3 error from:809
You can rename it, by changing the extension to aec. I would suggest this: OriginalFileName-ARF.aec
Then open it and see if it is okay. Then move the OriginalFileName.aec to an Old Drawings folder. Then Save As the OriginalFileName-ARF.aec as OriginalFileName.aec.