Comment 2 for bug 931350

It seems the config file has changed slightly and the new libvirt on Precise will not accept the one from Lucid. From libvirtd.log:

2012-02-21 11:10:38.183+0000: 11978: error : virDomainDefParseXML:7542 : unsupported configuration: Only the first console can be a serial port
2012-02-21 11:10:38.183+0000: 11978: error : virDomainDefParseXML:7542 : unsupported configuration: Only the first console can be a serial port

The xml config file for the vms created on Lucid contain:

    <console type='pty'>
      <target port='0'/>
    </console>
    <console type='pty'>
      <target port='0'/>
    </console>

The config file for a vm created under Precise contains:

    <serial type='pty'>
      <target port='0'/>
    </serial>
    <console type='pty'>
      <target type='serial' port='0'/>
    </console>

When changing the first console tag with serial, the Lucid vm becomes available for me. Thanks to Stefan Bader, who found the double console entry.