Dear juliavy,
This might be caused by a bug in ARCHICAD that the export process (to 3DS format) may fail when you have objects placed that use picture files (eg. Picture 21, Fireplace 21, etc.).
Please try deleting/hiding the above mentioned objects before the export, and if that doesn't help, try removing all objects (because there might be other objects using pictures like this).
I hope this helps,
Daniel Alexander Kovacs
Professional Services Consultant
GRAPHISOFT
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