Problem spawning instances

Hi guys it's me again :), this time I'm having trouble when I try to launch instances, this is the error that is appearing in nova-compute.log

2011-05-05 16:01:06,156 INFO nova [-] called setup_basic_filtering in nwfilter
2011-05-05 16:01:06,157 INFO nova [-] ensuring static filters
2011-05-05 16:01:06,276 ERROR nova.exception [-] Uncaught exception
(nova.exception): TRACE: Traceback (most recent call last):
(nova.exception): TRACE: File "/usr/lib/pymodules/python2.6/nova/exception.py", line 79, in _wrap
(nova.exception): TRACE: return f(*args, **kw)
(nova.exception): TRACE: File "/usr/lib/pymodules/python2.6/nova/virt/libvirt_conn.py", line 623, in spawn
(nova.exception): TRACE: self.firewall_driver.prepare_instance_filter(instance, network_info)
(nova.exception): TRACE: File "/usr/lib/pymodules/python2.6/nova/virt/libvirt_conn.py", line 2000, in prepare_instance_filter
(nova.exception): TRACE: self.add_filters_for_instance(instance, network_info)
(nova.exception): TRACE: File "/usr/lib/pymodules/python2.6/nova/virt/libvirt_conn.py", line 2031, in add_filters_for_instance
(nova.exception): TRACE: network_info)
(nova.exception): TRACE: File "/usr/lib/pymodules/python2.6/nova/virt/libvirt_conn.py", line 2012, in _filters_for_instance
(nova.exception): TRACE: for ip in mapping['ip6s']]
(nova.exception): TRACE: KeyError: 'ip6s'
(nova.exception): TRACE:
2011-05-05 16:01:06,276 ERROR nova.compute.manager [0SG0Z-DRW7A866Z250RQ myuser proj1] Instance '11' failed to spawn. Is virtualization enabled in the BIOS?
(nova.compute.manager): TRACE: Traceback (most recent call last):
(nova.compute.manager): TRACE: File "/usr/lib/pymodules/python2.6/nova/compute/manager.py", line 240, in run_instance
(nova.compute.manager): TRACE: self.driver.spawn(instance_ref)
(nova.compute.manager): TRACE: File "/usr/lib/pymodules/python2.6/nova/exception.py", line 85, in _wrap
(nova.compute.manager): TRACE: raise Error(str(e))
(nova.compute.manager): TRACE: Error: 'ip6s'

This is the nova.conf file:

--dhcpbridge_flagfile=/etc/nova/nova.conf
--dhcpbridge=/usr/bin/nova-dhcpbridge
--logdir=/var/log/nova
--state_path=/var/lib/nova
--lock_path=/var/lock/nova
--verbose
--s3_host=192.168.1.208
--rabbit_host=192.168.1.208
--cc_host=192.168.1.208
--ec2_url=http://192.168.1.208:8773/services/Cloud
--fixed_range=10.0.0.0/12
--network_size=88
--network_manager=nova.network.manager.FlatManager
--routing_source_ip=192.168.1.1
--FAKE_subdomain=ec2
--image_service=nova.image.glance.GlanceImageService
--glance_host=192.168.1.208
--glance_port=9292
--sql_connection=mysql://root:nova@192.168.1.208/nova

this is the network configuration /etc/network/interfaces

auto lo
iface lo inet loopback

# Networking for OpenStack Compute
auto br100

iface br100 inet dhcp
    bridge_ports eth0
    bridge_stp off
    bridge_maxwait 0
    bridge_fd 0

I'm running all the services on the same machine.

Cheers
Diego