Well, this is prbly too late to help the original post, but if anyone else is trying to hunt this problem down, this may help. I recently ran into the exact same error in a drawing file that I had been working on previously. The drawing would open properly, but when I would go to a different tab, model or ps, it would crash with the 'unhandled error' message. It had Xref's/image files that 'lost' the file path. I tried to detach the files, as they were no longer needed, saved the file to a new location, reopened the file, but i would have the same problem. The next step was to re-direct the file paths (in the image manager), audit and purge, and this apparently fixed the problem. I hope someone else that is getting frustrated with this error can utilize this info, as it caused me a great deal of headache!!!