Postgresql on 64bit Debian 4.0: libz.so.1 => not found

I need to get Postgresql installed on 64bit Debian 4.0.

Postgresql was installed as a part of the Trend IWSS web security suite, but
Postgresql doesn't seemt to work on 64bit Debian 4.

What happens is:

# /usr/iwss/PostgreSQL/bin/postgres
/usr/iwss/PostgreSQL/bin/postgres: error while loading shared libraries:
libz.so.1: cannot open shared object file: No such file or directory

The libaries:

# ldd /usr/iwss/PostgreSQL/bin/postgres
linux-gate.so.1 => (0xffffe000)
libz.so.1 => not found
libcrypt.so.1 => /lib32/libcrypt.so.1 (0xf7f68000)
libresolv.so.2 => /lib32/libresolv.so.2 (0xf7f55000)
libnsl.so.1 => /lib32/libnsl.so.1 (0xf7f3e000)
libdl.so.2 => /lib32/libdl.so.2 (0xf7f3a000)
libm.so.6 => /lib32/libm.so.6 (0xf7f16000)
libc.so.6 => /lib32/libc.so.6 (0xf7deb000)
/lib/ld-linux.so.2 (0xf7f9c000)

The libz.so.1 DOES exists at /usr/lib/libz.so.1 but Postgresql apparently
cannot use it.
How do I resolve this situation?
Any ideas?

Thanks