Try first with "dpkg --configure -a" which should finish any unfinished configurations.
When you apt-getted libxv1 did you try to put in unstable? As in "apt-get -t unstable install libxv1".
For what you have now I'd try with "dpkg -i --force-overwrite /var/cache/apt/archives/libxv1_4.3.0-7_i386.deb".