Can not bootstrap juju on a brand new Ubuntu 12.04 VM

[Haitao Jiang]

Hi, there

Since I have been having various problems with upgraded 12.04 (11.10),
I created a brand new VM from 12.04 ISO, did update and upgrade and
installed the juju, however,

$ juju bootstrap
2012-05-09 18:08:47,157 INFO Bootstrapping environment 'local'
(origin: distro type: local)...
2012-05-09 18:08:47,158 INFO Checking for required packages...
2012-05-09 18:08:50,061 INFO Starting networking...
Network default defined from /tmp/tmpVS3o07

error: Failed to start network default
error: internal error Network is already in use by interface virbr0

Command '['virsh', 'net-start', 'default']' returned non-zero exit status 1
2012-05-09 18:08:50,551 ERROR Command '['virsh', 'net-start',
'default']' returned non-zero exit status 1

------------

I rebooted after installing and change /etc/sysctl.conf, still have
these problems, really frustrated.

Thanks for any help

Haitao