I finally finished (kind of) the translation of 4.5.0.
The file ZhMsg.properties is not fully translated yet, the rest is OK.
I also fixed the spell check on the PHP side (see bug 14131 in http://bugzilla.zimbra.com/, it includes the patch).
As usual, here are the language files. A package with these files, the French date zimlet, the spell check fix, and a installation script can be downloaded from http://files.whitehatmail.fr/ (user invite, password invite), file Zimbra/zcs-fr-4.5.0.tgz.
I uploaded the files to SVN too (http://zimbra-xtras.svn.sourceforge....ta/French_fr/).
PS. Many thanks to Didier Laurent for helping me with my poor orthograph!