backing up packages

[aphro@portal.aphroland.org]

hi.

i am interested in doing something along the lines of:
dpkg --get-selections | awk '{print $1}' | dpkg-repack

to get debs of all of the existing software. some  of it
(less then 5 packages) are 3rd party, and i want to back
up what EXACTLY is on the system as opposed to download
the packages off a debian mirror and storing those.

however, the above command doesn't work too well. i get
a lot of these errors:
-- Creating control files
-- Copying files
-- Building package
dpkg-deb: building package `zlib1g' in `./zlib1g_1.1.3-5_i386.deb'.
-- Cleaning up
dpkg-repack: Errors were encountered in processing.
dpkg-repack: The package may not unpack correctly.
-- Creating control files
-- Copying files
-- Building package
dpkg-deb: building package `zoo' in `./zoo_2.10-7_i386.deb'.
-- Cleaning up
dpkg-repack: Errors were encountered in processing.
dpkg-repack: The package may not unpack correctly.

from the looks of it all of the packages are made, but
i am curious what could cause such an error? it happens
on virtually every package. listing the contents of a 
package such as zoo comes up with a buncha files that 
look right..is there a better way of automating the 
repacking of all installed packages? and/or is there
a way to verify the packages?

thanks

nate