In Libreoffice Writer by selecting the search menu item or pressing Ctrl+F doesn't open any search window.
When I want to search a string within a document I have to select the "search & replace" menu item or to press Ctrl+Alt+F.
It seems to be a version problem. I have installed (Fedora 16):
libreoffice-langpack-en-3.4.4.2-3.fc16.x86_64
libreoffice-opensymbol-fonts-3.4.4.2-3.fc16.noarch
libreoffice-xsltfilter-3.4.4.2-3.fc16.x86_64
libreoffice-writer-3.4.4.2-3.fc16.x86_64
libreoffice-ure-3.4.4.2-3.fc16.x86_64
libreoffice-core-3.4.4.2-3.fc16.x86_64
libreoffice-langpack-fr-3.4.4.2-3.fc16.x86_64
libreoffice-draw-3.4.4.2-3.fc16.x86_64
libreoffice-math-3.4.4.2-3.fc16.x86_64
libreoffice-pdfimport-3.4.4.2-3.fc16.x86_64
libreoffice-langpack-de-3.4.4.2-3.fc16.x86_64
libreoffice-impress-3.4.4.2-3.fc16.x86_64
libreoffice-kde-3.4.4.2-3.fc16.x86_64
libreoffice-presenter-screen-3.4.4.2-3.fc16.x86_64
libreoffice-calc-3.4.4.2-3.fc16.x86_64
libreoffice-langpack-it-3.4.4.2-3.fc16.x86_64
libreoffice-graphicfilter-3.4.4.2-3.fc16.x86_64