BCP Flat File Empty fields lost

I have a problem with BCP not copying empty fields.

I'm using BCP to copy a flat text file, with 10 fixed length fields,
to a SQL6.5 database table I created expressly for the purpose:
bcp db..dbtable in c: extfile.txt /Usa /Ppasswd /Sserver

and then after setting up the format file:

bcp db..dbtable in c: extfile.txt /f /Usa /Ppasswd /Sserver

I then perform query:
USE db
Select *
FROM dbtable

The first five rows, whose ten columns are all populated, displays perfectly.
The next line is displaced because there is a field which was not populated in the (fixed length field) text file.

What is the solution?
Thanks, Michael