Hey,
Sadly 280x are wrong, not sure why... Will update it soon(Managed to get 290hash/s with stock 280x)
Anyway I managed to get even better results from 750ti - reports 0,38 khash/s:
cudaminer.exe -a scrypt-jane:YAC -H 2 -L 8 -i 0 -l t64x1 -b 4096 -m 1
can you share batch file for 290h/s to try?