I am not surprised it doesn't work. (Speaking naively) 9i export can produce stuff from new facilities that 8i can't understand because they didn't exist when 8i was born.

The rule is, when going from version X to version Y:
- export with the lower of X and Y, from X
- import with Y, into Y
(see Tom Kyte 1-on-1 p.353)

So:
- from 9i to 8i, both export and import need to be 8i
- from 8i to 9i, export with 8i, import with 9i