Unable to select Intel in PRIME Profiles within nvidia-settings

1) The release of Ubuntu you are using, via 'lsb_release -rd' or System -> About Ubuntu
Description: Ubuntu Trusty Tahr (development branch)
Release: 14.04

2) The version of the package you are using, via 'apt-cache policy pkgname' or by checking in Software Center
nvidia-331:
  Installed: 331.38-0ubuntu3
  Candidate: 331.38-0ubuntu3
  Version table:
 *** 331.38-0ubuntu3 0
        500 http://mirror.bytemark.co.uk/ubuntu/ trusty/restricted amd64 Packages
        100 /var/lib/dpkg/status

3) What you expected to happen
To be able to select Intel (Power Saving Mode) from the nvidia/intel list

4) What happened instead
Alert window appears with a traceback.
The same traceback is visible in the terminal:

iain-laptop ~ $ nvidia-settings
** Message: PRIME: Laptop detected
** Message: PRIME: is it supported? yes

ERROR: Traceback (most recent call last):
       File "/usr/lib/python3/dist-packages/dbus/bus.py", line 175, in activate_name_owner
       return self.get_name_owner(bus_name)
       File "/usr/lib/python3/dist-packages/dbus/bus.py", line 361, in get_name_owner
       's', (bus_name,), **keywords)
       File "/usr/lib/python3/dist-packages/dbus/connection.py", line 651, in call_blocking
       message, timeout)
       dbus.exceptions.DBusException: org.freedesktop.DBus.Error.NameHasNoOwner: Could not get owner of name 'com.ubuntu.ScreenResolution.Mechanism': no such name
       During handling of the above exception, another exception occurred:
       Traceback (most recent call last):
       File "/usr/share/screen-resolution-extra/nvidia-prime.py", line 55, in <module>
       conf = get_prime_service()
       File "/usr/share/screen-resolution-extra/nvidia-prime.py", line 34, in get_prime_service
       service_object = dbus.SystemBus().get_object(SERVICE_NAME, OBJECT_PATH)
       File "/usr/lib/python3/dist-packages/dbus/bus.py", line 241, in get_object
       follow_name_owner_changes=follow_name_owner_changes)
       File "/usr/lib/python3/dist-packages/dbus/proxies.py", line 248, in __init__
       self._named_service = conn.activate_name_owner(bus_name)
       File "/usr/lib/python3/dist-packages/dbus/bus.py", line 180, in activate_name_owner
       self.start_service_by_name(bus_name)
       File "/usr/lib/python3/dist-packages/dbus/bus.py", line 278, in start_service_by_name
       'su', (bus_name, flags)))
       File "/usr/lib/python3/dist-packages/dbus/connection.py", line 651, in call_blocking
       message, timeout)
       dbus.exceptions.DBusException: org.freedesktop.DBus.Error.Spawn.ChildExited: Launch helper exited with unknown return code 1

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: nvidia-331 331.38-0ubuntu3
ProcVersionSignature: Ubuntu 3.13.0-7.25-generic 3.13.1
Uname: Linux 3.13.0-7-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.13.2-0ubuntu2
Architecture: amd64
CurrentDesktop: Unity
Date: Wed Feb 5 20:55:48 2014
InstallationDate: Installed on 2014-01-23 (13 days ago)
InstallationMedia: Ubuntu 14.04 LTS "Trusty Tahr" - Alpha amd64 (20140123)
SourcePackage: nvidia-graphics-drivers-331
UpgradeStatus: No upgrade log present (probably fresh install)