Minecraft closes on "Building Terrain..." Ubuntu 10.04

Fresh installed Ubuntu 10.04. Loving it. I appear to have an updated Java already... I downloaded the jar file from the website, and created a launcher for it. Log in no problem. I click single player, and select an empty world. It starts loading up where it says "Building terrain..." and then just disappears. gone. nothing. I am assuming I am missing some sort of Java file. I'm not great with Ubuntu, trying to give it a shot. Anyone else have this issue?