Deleting Flavor gives Error [delete() takes exactly 2 arguments (3 given)]

Having create a flavor per:
# nova-manage instance_type create m1.xxlarge 32768 16 320 0 0 0

Was displaying correctly in Dashboard, then clicking on red [Delete] button gave rise to error screen output in browser:

TypeError at /syspanel/flavors/
delete() takes exactly 2 arguments (3 given)
Request Method: POST
Request URL: https://stack.server.lan/syspanel/flavors/
Django Version: 1.3.1
Exception Type: TypeError
Exception Value:
delete() takes exactly 2 arguments (3 given)
Exception Location: /usr/src/openstack/horizon/horizon/horizon/api/nova.py in flavor_delete, line 205
Python Executable: /usr/bin/python
Python Version: 2.7.2
Python Path:
['/usr/src/openstack/horizon/openstack-dashboard/dashboard/wsgi/../..',
 '/usr/src/openstack/horizon/.horizon-venv/lib/python2.7/site-packages/distribute-0.6.19-py2.7.egg',
 '/usr/src/openstack/horizon/.horizon-venv/lib/python2.7/site-packages/pip-1.0.2-py2.7.egg',
 '/usr/src/openstack/horizon/.horizon-venv/src/python-quantumclient',
 '/usr/src/openstack/horizon/.horizon-venv/src/python-novaclient',
 '/usr/src/openstack/horizon/.horizon-venv/src/python-keystoneclient',
 '/usr/src/openstack/horizon/.horizon-venv/src/glance',
 '/usr/src/openstack/horizon/horizon',
 '/usr/src/openstack/horizon/.horizon-venv/lib/python2.7/site-packages/MySQL_python-1.2.3-py2.7-linux-x86_64.egg',
 '/usr/src/openstack/horizon/.horizon-venv/lib/python2.7/site-packages',
 '/usr/src/openstack/horizon',
 '/usr/local/lib/python2.7/dist-packages/swiftkeystone2-0.1-py2.7.egg',
 '/usr/lib/python2.7',
 '/usr/lib/python2.7/plat-linux2',
 '/usr/lib/python2.7/lib-tk',
 '/usr/lib/python2.7/lib-old',
 '/usr/lib/python2.7/lib-dynload',
 '/usr/local/lib/python2.7/dist-packages',
 '/usr/lib/python2.7/dist-packages',
 '/usr/lib/python2.7/dist-packages/PIL',
 '/usr/lib/python2.7/dist-packages/gtk-2.0',
 '/usr/lib/pymodules/python2.7',
 '/usr/src/openstack/horizon/openstack-dashboard/dashboard']
Server time: Tue, 31 Jan 2012 15:44:27 +1000