In "Release Notes LibreOffice 3.6.1 Final (2012-08-29)" I fond the hint concerning the Workaround for the 3.4 uninstall Bug 36677 - Uninstall Problems with MSI on Windows 7 64bit: "For Windows users that have LibreOffice prior to version 3.4.5 installed, either uninstall that beforehand, or upgrade to 3.4.5. Otherwise, the upgrade to 3.6.1 may fail." That hint is correct, but useless, 3.4.5 is no longer available via LibO site. So a link to a mirror with that version (for example <http://ftp.uni-muenster.de/pub/software/LibreOffice/stable/> or our archive (I forgot the URL) will be required.
I fixed it in SilverStripe.