Hello geeks, 
    I installed an Ubuntu 10.04 VM on
          Centos 5.5 domain0.
    To reach my goal, I upgraded pygrub
          to be able to read the grub2.
    First problem : under vnc, I do not
          have the mouse support :/ !
    I upgraded xen to 4.0.1 with the
          "www.gitco.de" yum repository.
    Ok I have now the mouse support,
          yeeaaaah !
    But my virt-manager does not work !
    I have this error : 
    "Unable to open a connection to the
          hypervisor"
    "libvirt.libvirtError unable to
          connect to 'localhost:8000' : Connection refused"
    I do not use virt-manager but I want
          to understand this error ;) !
    Does someone have an idea ?