Launching instance fails: no tty present and no askpass program specified (qemu-nbd)

Fresh server (Ubuntu 10.10), installed from trunk (nova-compute: 2011.1~bzr562-0ubuntu0ppa1~maverick1
), no modifications

Following error occurs when trying to launch any instance: (snippet from nova-compute.log)

(nova.virt.libvirt_conn 2011.1-workspace:tarmac-20110114001914-5vbfe8sm72xr2py4): WARNING [N/A] instance instance-0000000e: ignoring error injecting data into image ami-tty (Unexpected error while running command.
Command: sudo qemu-nbd -c /dev/nbd7 /var/lib/nova/instances/instance-0000000e/disk
Exit code: 1
Stdout: ''
Stderr: 'sudo: no tty present and no askpass program specified\n')
libvir: QEMU error : operation failed: failed to retrieve chardev info in qemu with 'info chardev'
(nova.exception 2011.1-workspace:tarmac-20110114001914-5vbfe8sm72xr2py4): ERROR [N/A] Uncaught exception
(nova.exception): TRACE: Traceback (most recent call last):
(nova.exception): TRACE: File "/usr/lib/pymodules/python2.6/nova/exception.py", line 82, in _wrap
(nova.exception): TRACE: return f(*args, **kw)
(nova.exception): TRACE: File "/usr/lib/pymodules/python2.6/nova/virt/libvirt_conn.py", line 382, in spawn
(nova.exception): TRACE: self._conn.createXML(xml, 0)
(nova.exception): TRACE: File "/usr/lib/python2.6/dist-packages/libvirt.py", line 1289, in createXML
(nova.exception): TRACE: if ret is None:raise libvirtError('virDomainCreateXML() failed', conn=self)
(nova.exception): TRACE: libvirtError: operation failed: failed to retrieve chardev info in qemu with 'info chardev'
(nova.exception): TRACE:
(nova.compute.manager 2011.1-workspace:tarmac-20110114001914-5vbfe8sm72xr2py4): ERROR [34U5K1XW3K3RH2JEP138 admin admin] instance 14: Failed to spawn
(nova.compute.manager): TRACE: Traceback (most recent call last):
(nova.compute.manager): TRACE: File "/usr/lib/pymodules/python2.6/nova/compute/manager.py", line 208, 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 88, in _wrap
(nova.compute.manager): TRACE: raise Error(str(e))
(nova.compute.manager): TRACE: Error: operation failed: failed to retrieve chardev info in qemu with 'info chardev'
(nova.compute.manager): TRACE:
libvir: QEMU error : Domain not found: no domain with matching name 'instance-0000000e'