pkg_add and me

[Mauricio]

         I want to upgrade the version of libiconv that is in this
machine (PC running freebsd 5.1).  So, I try pkg_add:

daffy# pkg_add libiconv-1.9.1_3.tgz
pkg_add: package 'libiconv-1.9.1_3' or its older version already
installed
daffy#

Ok then, I force it to be installed (-f option).  All I get in the end
is *two* entries of libiconv according to pkg_info:

daffy# pkg_info
XFree86-FontServer-4.3.0_1 XFree86-4 font server
XFree86-NestServer-4.3.0_1 XFree86-4 nested X server
[...]
libiconv-1.8_2      A character set conversion library
libiconv-1.9.1_3    A character set conversion library

Why can't it put the latest version in place of the older one?  I 
even tried to uninstall the old one first:

daffy# pkg_delete libiconv-1.8_2
pkg_delete: package 'libiconv-1.8_2' is required by these other packages
and may not be deinstalled:
gettext-0.11.5_1
gmake-3.80
lynx-2.8.5d14
daffy#

but, as you can see, it does not seem to like that.  Someone 
suggested me to install portupgrade as follows:

>  cd /usr/ports/sysutils/portupgrade
>  make install clean
>  rehash
>  <cvsup your ports tree>
>  portupgrade libiconv
>
>  should do all you need. :)
>
>

    I did the above, but ended up having two instances of libiconv:

daffy# pkg_info
[...]
imake-1.0           Imake and other utilities from XFree86
imake-4.3.0         Imake and other utilities from XFree86
jpeg-6b_1           IJG's jpeg compression utilities
libiconv-1.8_2      A character set conversion library
libiconv-1.9.1_3    A character set conversion library
libtool-1.3.4_4     Generic shared library support script
libtool-1.3.5_1     Generic shared library support script
lrzsz-0.12.20       Receive/Send files via X/Y/ZMODEM protocol. 
[...]
daffy#

How come?