Error while creating VM using virt-manager on Xen.

Unable to complete install: 'POST operation failed: xend_post: error from xen daemon: (xend.err "Error creating domain: 'NoneType' object has no attribute 'rfind'")'

DETAILS->
Unable to complete install '<class 'libvirt.libvirtError'> POST operation failed: xend_post: error from xen daemon: (xend.err "Error creating domain: 'NoneType' object has no attribute 'rfind'")
Traceback (most recent call last):
  File "/usr/share/virt-manager/virtManager/create.py", line 1555, in do_install
    dom = guest.start_install(False, meter = meter)
  File "/usr/lib/pymodules/python2.6/virtinst/Guest.py", line 973, in start_install
    return self._do_install(consolecb, meter, removeOld, wait)
  File "/usr/lib/pymodules/python2.6/virtinst/Guest.py", line 1038, in _do_install
    "install")
  File "/usr/lib/pymodules/python2.6/virtinst/Guest.py", line 1009, in _create_guest
    dom = self.conn.createLinux(start_xml, 0)
  File "/usr/lib/python2.6/dist-packages/libvirt.py", line 1277, in createLinux
    if ret is None:raise libvirtError('virDomainCreateLinux() failed', conn=self)
libvirtError: POST operation failed: xend_post: error from xen daemon: (xend.err "Error creating domain: 'NoneType' object has no attribute 'rfind'")
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