I was getting the very same errors the ubutntu fellows got. To me it was that I used blackdown java - it didn't work. Changing to sun 1.6 solved all issues.
hagen ~ # eselect java-vm list
Available Java Virtual Machines:
[1] blackdown-jdk-1.4.2
[2] sun-jdk-1.5
[3] sun-jdk-1.6 system-vm
hagen ~ #
not a support question