Well, I just got word that the problem was fixed...
They installed a demo version of J so they could open the files. (Long story short), She realised that she could then open it in SE. She then tested it by deleting a cell (block) of a previous contractor's logo that was placed on the client's drawings. After that, all is well. Something in that cell was screwy. Don't know what it was...don't care. It's fixed. Thanks everyone.