Several thoughts..
1. You are trying to move data from a proprioritory field type to another proprioritory field type. Deep down FMP converts all embedded images to PICT formatted images. Who knows what format is used in a BLOB file. My fix would be to script the BLOB image to a file, let's call it import_me.jpg. Then script FMP to insert (not import) import_me.jpg into the Container field in the record. Move to the next record in both databases and reapeat.
2. My second thought is that is generally bad style to embed images into the database. Before you go crazy on me, I realize the need is there, but instead of embedding the image linking to an image is a better approach, the only catch is that you have to make sure that all users have file level access to your 'shared graphics' folder.
thanks,
Joe King