Does LO Support Java x64?
You need to match Java and LibreOffice.
If you are using LibreOffice on Microsoft Windows LibreOffice is built for 32bit so you need to install x86 Java Runtime (32bit). You can install multiple versions of Java and pick the 32bit from the LibreOffice settings.
On other platforms, if you are using 64bit release of LibreOffice, you should select the x64 Java Runtime (64bit).
Yes. As @grakic has indicated in the comment above the Java version (32bit / x86 vs 64bit / x64) must match the build version of LO. For GNU/Linux there are builds to match either Java version. For MacOS LO v3.x-v4.1.4.1 Java 32bit / x86 is required, while for LO v4.1.4.2+ there are builds to match either Java version. For Windows the Java version needs to be 32bit / x86. Also refer these questions: