apt-get -f install question..

[Ishwar Rattan <ishwar@pali.cps.cmich.edu>]

After trying to install scm (scheme interpreter) failure, apt-get
suggested to try 'apt-get -f install' but this also resulted in error
(message shown below). Is there a way out?

-ishwar
--------
apt-get -f install
Reading Package Lists... Done
Building Dependency Tree... Done
Correcting dependencies... Done
The following extra packages will be installed:
  libxt6
  The following packages will be upgraded:
    libxt6
    1 upgraded, 0 newly installed, 0 to remove and 699 not upgraded.
    61 not fully installed or removed.
    Need to get 0B/312kB of archives.
    After unpacking 61.4kB of additional disk space will be used.
    Do you want to continue? [Y/n] y
    Preconfiguring packages ...
    (Reading database ... 113233 files and directories currently installed.)
    Preparing to replace libxt6 4.3.0.dfsg.1-6 (using .../libxt6_4.3.0.dfsg.1-8_i386.deb) ...
    Unpacking replacement libxt6 ...
    dpkg: error processing /var/cache/apt/archives/libxt6_4.3.0.dfsg.1-8_i386.deb (--unpack):
     trying to overwrite `/usr/X11R6/lib/X11/app-defaults', which is also in package xnview

Errors were encountered while processing:
/var/cache/apt/archives/libxt6_4.3.0.dfsg.1-8_i386.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)
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