Comment 2 for bug 847110

Terminal log shows

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Preparing to replace foo2zjs 20071205-0ubuntu3.1 (using .../foo2zjs_20100210-0ubuntu4_i386.deb) ...
8.04.1 (using .../firefox-3.0-gnome-support_3.6.22+build2+nobinonly-0ubuntu0.10.04.1_all.deb) ...
dpkg: error processing /var/cache/apt/archives/foo2zjs_20100210-0ubuntu4_i386.deb (--unpack):
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Seems that the .deb package file is broken. Run

sudo apt-get clean
sudo apt-get install -f
sudo apt-get update
sudo apt-get upgrade

in a terminal window to get your system updated and consistent. Re-open this bug if this problem occurs again then.