I have a 64-bit processor, but prefer to run in 32-bits because everything just
works, whereas you are bound to be disappointed if you expect 64-bit Ubuntu to
do multimedia as simply and as easily. It can be an exercise in frustration.

Java will work, but you will find that it is hit or miss. For example you might
get it going in one application, but another will tell you that it isn't
installed. This does not happen with 32-bit. Flash is worse. It is only
available in 32-bit so you need to install lots of things such as ndiswrapper
and lots of 32-bit utilities and libraries. Real audio is worse still and
Quicktime will only work through Wine.

It is recommended that you run 32-bit versions of Firefox and multimedia apps in
order to avaoid potential problems. Here is a guide:
ubuntuforums.org/showthread.php

This may seem like a disappointment but 64-bit isn't supported as widely as
32-bit and your fellow 64-bit users feel your pain.