ERROR: invalid input syntax for type timestamp: ""

Hello,

I am using Postgres version 8.3.17 on one of my database server. I have
received a .sql dump file from my client. Which is supposed to be taken
from a Postgres 8.3.7 db. Now, I have created an empty database and I am
trying to restore the .sql file with command psql command. After few GBs
of restoration, I am getting an error -

ALTER TABLE

SET

SET

ERROR: invalid input syntax for type timestamp: ""

CONTEXT: COPY job_step_history, line 16211941, column start_time: ""

I tried printing this line no - 16211941 from the .sql dump file with
command - sed -n "16211941 p" <filename.sql> . The row has values -

17338525 1 309 6 205636 2009-09-04 22:02:46.199
1 2009-09-04 22:02:46.198 1 \N

What can be the possible cause for this error? Please help.

Regards,

Swanand