Error upgrading xlibs to testing

[nathan_salwen@ncsu.edu]

after editing the /etc/apt/sources.list I ran
> apt-get update
> apt-get dist-upgrade

and then got the following error


Preparing to replace xlibs 4.1.0-16 (using .../xlibs_4.2.1-3_i386.deb) ...
Unpacking replacement xlibs ...
dpkg: error processing /var/cache/apt/archives/xlibs_4.2.1-3_i386.deb (--unpack):
 trying to overwrite `/usr/X11R6/lib/X11/app-defaults', which is also in package dialdcost
Analyzing /usr/X11R6/lib/X11/app-defaults:
drwxr-xr-x   13 root     root         4096 Mar 22 17:22 /usr
drwxr-xr-x    6 root     root         4096 Jul 26  2002 /usr/X11R6
drwxr-xr-x    4 root     root         4096 Mar 22 17:24 /usr/X11R6/lib
drwxr-xr-x   12 root     root         4096 Mar 22 17:24 /usr/X11R6/lib/X11
drwxr-xr-x    2 root     root         4096 Mar 22 17:24 /usr/X11R6/lib/X11/app-defaults
ERROR: /usr/X11R6/lib/X11/app-defaults is not a symbolic link.  The package 
preinst script should have failed.
Please report the package name, version, and the text of the above error 
message(s) to <debian-x@lists.debian.org>.
dpkg: error while cleaning up:
 subprocess post-installation script returned error exit status 1

only after running 
> dpkg -r dialdcost
did
> apt-get install xlibs
run ok.