cannot upgrade cupsys

Binary package hint: cupsys

will@crystal:~$ sudo apt-get upgrade
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages will be upgraded:
  cupsys
1 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
Need to get 1820kB of archives.
After unpacking 1393kB disk space will be freed.
Do you want to continue [Y/n]?
Get: 1 http://gb.archive.ubuntu.com gutsy/main cupsys 1.3.2-1ubuntu4 [1820kB]
Fetched 1820kB in 43s (42.1kB/s)
Preconfiguring packages ...
(Reading database ... 110274 files and directories currently installed.)
Preparing to replace cupsys 1.3.2-1ubuntu1 (using .../cupsys_1.3.2-1ubuntu4_i386.deb) ...
Ignoring nonregistered document cupsys
 * Stopping Common Unix Printing System: cupsd [ OK ]
Unpacking replacement cupsys ...
dpkg: error processing /var/cache/apt/archives/cupsys_1.3.2-1ubuntu4_i386.deb (--unpack):
 trying to overwrite `/usr/share/doc/libcupsys2/CREDITS.txt', which is also in package libcupsys2
dpkg-deb: subprocess paste killed by signal (Broken pipe)
 * Starting Common Unix Printing System: cupsd [ OK ]
Errors were encountered while processing:
 /var/cache/apt/archives/cupsys_1.3.2-1ubuntu4_i386.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)
will@crystal:~$

ProblemType: Bug
Architecture: i386
Date: Fri Oct 5 10:18:59 2007
DistroRelease: Ubuntu 7.10
ExecutablePath: /usr/bin/yelp
NonfreeKernelModules: nvidia
Package: yelp 2.20.0-0ubuntu2
PackageArchitecture: i386
ProcCmdline: yelp
ProcCwd: /home/will
ProcEnviron:
 PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games
 LANG=en_GB.UTF-8
 SHELL=/bin/bash
SourcePackage: yelp
Uname: Linux crystal 2.6.22-12-generic #1 SMP Sun Sep 23 18:11:30 GMT 2007 i686 GNU/Linux