This is a problem for me, as a user/admin of a Sonicwall SSL VPN 2000. The SSL VPN devices have a great portal, which allow you to create all sorts of Java enabled links to do things like remote desktop, and browse file share. However it appears that none of these work with the open sourced java components that ship with Ubuntu 10.4.
So, to resolve this, I first removed openjdk (and all associated stuff) using synaptic package manager
then do the following at a command prompt
then you should be all set.
sudo add-apt-repository "deb http://archive.canonical.com/ lucid partner"
sudo apt-get update
sudo apt-get install sun-java6-jdk
sudo apt-get install sun-java6-jre
sudo apt-get install sun-java6-plugin