Solved open network files (only if you install LibreOffice 4.4 (4.4.6 on Ubuntu 12.04 in my case) using dpkg):
Put in the terminal:
sudo sed -i ‘s/X-GIO-NoFuse=true/#X-GIO-NoFuse=true/’ /opt/libreoffice4.4/share/xdg/*
Strange:
after installing LibreOffice (4.4.6 on Ubuntu 12.04 in my case) using dpkg, I had to restart the PC to see the changes