omreport on Ubuntu 14.04 (trusty) not working.

I use Nagios to monitor hardware state using omreport (via the check_openmanage script).

Since upgrading to 14.04 omreport can no longer see most hardware. For example:

sudo /opt/dell/srvadmin/sbin/omreport chassis volts
Error! No voltage probes found on this system.
sudo /opt/dell/srvadmin/sbin/omreport chassis temps
Error! No temperature probes found on this system.
sudo /opt/dell/srvadmin/sbin/omreport chassis fans
Error! No fan probes found on this system.

however it can find other hardware:

sudo /opt/dell/srvadmin/sbin/omreport chassis bios
BIOS Information

Manufacturer : Dell Inc.
Version      : 1.5.2
Release Date : 03/11/2013

sudo /opt/dell/srvadmin/sbin/omreport storage controller
 Controller  PERC H310 Mini (Embedded)

Controllers
ID                                            : 0
Status                                        : Ok
Name                                          : PERC H310 Mini
Slot ID                                       : Embedded
...
...

Why have some of the chassis sensors stopped working? I'm using this source:

cat /etc/apt/sources.list.d/linux.dell.com.sources.list
deb linux.dell.com/.../latest /