zlib1g vs zlib1g-dev (potato)

[will trillich <will@serensoft.com>]

i've got two debian boxes recently fsckd and partitioned and
installed via potato ISO cd roms.

on one, i downloaded the vpnd tarball and did
	# ./configure
	# make
and voila, no troubles.

[vpnd from http://www.crosswinds.net/~anstein/unix/vpnd.html ]

on the other debian box, i get
	# ./configure
	Please install the package zlib 1.1.3 or later.
	You can find it at:
	http://www.cdrom.com/pub/infozip/zlib/
	If your system has libz.so installed please
	make sure that the zlib-devel rpm is installed,
	too.
	Building vpnd with runtime compression disabled.

	# apt-get install zlib1g-dev
	Reading Package Lists... Done
	Building Dependency Tree... Done
	Some packages could not be installed. This may mean that you have
	requested an impossible situation or if you are using the unstable
	distribution that some required packages have not yet been created
	or been moved out of Incoming.

	Since you only requested a single operation it is extremely likely that
	the package is simply not installable and a bug report against
	that package should be filed.
	The following information may help to resolve the situation:

	Sorry, but the following packages have unmet dependencies:
	  zlib1g-dev: Depends: zlib1g (= 1:1.1.3-5) but 1:1.1.3-9 is to be installed

my /etc/apt/sources.list are set to potato:
	#deb file:/cdrom stable main
	deb http://http.us.debian.org/debian potato main contrib non-free
	deb http://non-us.debian.org/debian-non-US/ potato/non-US main contrib non-free

1) why would zlib1g-dev and zlib1g versions not match?
2) what method could i have implemented to get one debian box to compile vpnd,
	but not the other? tres bizarre.