I noticed one of the recent FAQ in OVM forum is about console.
OTN Discussion Forums : Oracle VM Server for x86
vnc console not running on Oracle VM 3.1.1
One of the variable for running console is Java version. I myself hit the bug below on Windows with JDK1.7
This is Windows only bug. I had success with JDK1.7 on Linux.
Bug ID: 7191616 javaws.exe crashes when starting jnlp file
jnlp file provided in the steps to reproduce always crashes javaws.exe in Java 7 Update 6.
No problems in Update 4