The workaround is to save on your disk then copy the file to your flash disk out of Sweet Home 3D.
As your suggestion I do: Copy the file directly from my HD to Flash disk; but it appears:" ERROR COPYING FILE OR FOLDER ...CANNOT COPY {FILE-NAME}: the directory or file cannot be created "
So it still not works.
Another questions: I need only the plan. Can I save only the plan individually as a JPG file? Because I need only the plan for my project not the 3D.