ArcMap does not include a preview or thumbnail with its EPS export files. Graphics applications use this preview to display the file. In its absence, you will only see the bounding box of the EPS file.
The file will print correctly even though you cannot see or edit it.
This problem affects Illustrator only if the Place command is used to import the file. Use the Open command to import the EPS as an editable graphics file. Freehand cannot import an ArcMap EPS as an editable file.