DoIT has confirmed a known issue that affects faculty trying to export an old Blackboard course and import it into a new, empty shell:
The export works fine, but if the resulting file is larger than 250 MB, faculty cannot import it. The process will return a "time out" error message.
Other schools running version 9.1 have reported this issue, but until Blackboard releases a fix and we have tested it, the work around is for faculty to submit an RT Ticket with a copy of the error message in the body of the ticket requesting that DoIT import the old course.