Strange number of line while restoring dump

Hello folks!
I'm using postgresql-9.0 on linux. While i was restoring backup from
plain dump, it stopped with message:
"
2010-09-28 21:30:29 CEST BAZA:netams USER:netams VTID:7/3952 ERROR:
null value in column "duration" violates not-null constraint
2010-09-28 21:30:29 CEST BAZA:netams USER:netams VTID:7/3952 CONTEXT:
COPY netflow, line -96891802: "\N   \N      11310512        \N
    \N  \N      \N      \N      \N      \N"
"
I don't know why there is negative number "line -96891802"?
Dump contains data from one table, there is used sql query "copy" to
insert them to db. File isn't small, it has size 450GB.
Thank you for help.
Regards,
Marcin