Comment 117 for bug 842566

omvsj: that's due to the upgrade to libreoffice 3.4.5 it needs other fixes (already in precise).

So or you backport bamf (just grab the bamf precise packages) or you can "fix" it by manually editing the /usr/share/applications/libreoffice-*.desktop files changing the Exec value to something like "libreoffice -writer %U" (instead of "libreoffice --writer %U", i.e. remove one dash char). You can just save these files in ~/.local/share/applications not to worry about upgrades or if you don't want to edit them system-wide.