Despite that I've been using my own image and for sure I haven't had such errors before, it seems that after dist-upgrade I was also lacking pl_pl (ISO-8859-1) - 'dpkg-reconfigure locales' - in which i generated pl_PL (ISO one) and set pl_PL.UTF-8 as default - also did the trick for me.

Warnings are gone, but now, polish language special characters aren't properly printed in terminal, but it's minor glitch.

just for the records - 'apt-get purge libreoffice', 'rm -r /home/user/.libreoffice' and 'apt-get install libreoffice -t squeeze-backports' did the trick about running LibreOffice from user, so now shortcuts (so, running through 'debbie libreoffice') are working flawlessly.

/Estel