Couldn't run instance due to dnsmasq error.

I couldn't run instance due to the following error.

(nova.root 2011.1-workspace:tarmac-20110115022500-fcgl1yga6csc221i):
ERROR [N/A] Exception during message handling
(nova.root): TRACE: Traceback (most recent call last):
(nova.root): TRACE: File "/usr/lib/pymodules/python2.6/nova/rpc.py", line 191, in receive
(nova.root): TRACE: rval = node_func(context=ctxt, **node_args)
(nova.root): TRACE: File "/usr/lib/pymodules/python2.6/nova/network/manager.py", line 143, in set_network_host
(nova.root): TRACE: self._on_set_network_host(context, network_id)
(nova.root): TRACE: File "/usr/lib/pymodules/python2.6/nova/network/manager.py", line 570, in _on_set_network_host
(nova.root): TRACE: self.driver.update_dhcp(context, network_id)
(nova.root): TRACE: File "/usr/lib/pymodules/python2.6/nova/network/linux_net.py", line 267, in update_dhcp
(nova.root): TRACE: _execute(command, addl_env=env)
(nova.root): TRACE: File "/usr/lib/pymodules/python2.6/nova/network/linux_net.py", line 328, in _execute
(nova.root): TRACE: return utils.execute(cmd, *args, **kwargs)
(nova.root): TRACE: File "/usr/lib/pymodules/python2.6/nova/utils.py", line 147, in execute
(nova.root): TRACE: cmd=cmd)
(nova.root): TRACE: ProcessExecutionError: Unexpected error while running command.
(nova.root): TRACE: Command: sudo -E dnsmasq --strict-order
--bind-interfaces --conf-file=
--pid-file=/var/lib/nova/networks/nova-br100.pid
--listen-address=10.0.0.1 --except-interface=lo
--dhcp-range=10.0.0.3,static,120s
--dhcp-hostsfile=/var/lib/nova/networks/nova-br100.conf
--dhcp-script=/usr/bin/nova-dhcpbridge --leasefile-ro
(nova.root): TRACE: Exit code: 2
(nova.root): TRACE: Stdout: ''
(nova.root): TRACE: Stderr: '\ndnsmasq: failed to bind listening socket for 10.0.0.1: Address already in use\n'
(nova.root): TRACE:
(nova.rpc 2011.1-workspace:tarmac-20110115022500-fcgl1yga6csc221i):
ERROR [N/A] Returning exception Unexpected error while running command.

The version I used is 2011.1~bzr569-0ubuntu0ppa1~maverick3, and the flag network_manager is VlanManager.

Please give me some advices.

Thank you.