even after laboriously following previous post, cannot cast from char to int

Hey,

Re casting char columns to int, I've worked all the proposed solutions
from previous
post-gres mailing list
posts<http://archives.postgresql.org/pgsql-general/2010-02/msg01078.php>,
but to no avail.

None of the ALTER TABLE proposed fixes worked for me, and now I have a new
INTEGER type column created, I execute the following:

UPDATE zip_code_data SET county_fips_rev = CAST(county_fips as INTEGER);

...and this is what I get:

ERROR: invalid input syntax for type numeric: " "

What is this telling me?

Thanks,

Lille