problem with my LaCie HD

I'm have a problem with my lacie 160g HD. Several files (large imovie ones) appear in finder, but without an icon. if you click on them they disappear and you cannot access them. I mainly use the drive as a backup to my powerbook. It is formatted as Mac OS extended (journaled). If I use disk utilities to verify or repair I get this error message

Repairing disk for “Robecq HD”
Mounting Disk(S,"Checking HFS Plus volume.",0)
Checking Extents Overflow file.
Checking Catalog file.
Invalid sibling link
Invalid B-tree Header
Invalid map node
Checking Catalog hierarchy.
Missing thread record (id = 22253)
Missing thread record (id = 22569)
Missing thread record (id = 23124)
Missing thread record (id = 23172)
Missing thread record (id = 23682)
Missing thread record (id = 23743)
Missing thread record (id = 23757)
Missing thread record (id = 23749)
Missing thread record (id = 23927)
Missing thread record (id = 23761)
Invalid volume file count
(It should be 18066 instead of 18065)
Checking volume bitmap.
Volume Bit Map needs minor repair
Checking volume information.
Invalid volume free block count
(It should be 21692154 instead of 18300172)
Repairing volume.
The volume Robecq HD could not be repaired.

Error: The underlying task reported failure on exit (-9972)

Repair attempted on 1 volume
0 HFS volumes repaired
1 volume could not be repaired

How can I recover my files and repair the HD?
any ideas?

No ideas? an ideas on where I could look?
Thanks