[CentOS] yum / rpm kernel problems - CentOS 7.2

This is the second time I have come across a problem with yum / rpm and 
kernel packages with CentOS 7.
I install CentOS7 and do a yum update
I add elrepo epel and virtualbox repos
I install Virtualbox-5.0
It fails to install
it give a message similar to :
- WARNING: The vboxdrv kernel module is not loaded. Either there is no 
module
          available for the current kernel (3.10.0-327.el7.x86_64) or it 
failed to
          load. Please recompile the kernel module and install it by

            sudo /sbin/rcvboxdrv setup

          You will not be able to start VMs until this problem is fixed.
5.0.14r105127

As I had done a yum update the kernel was actually 3.10.0-327.4.5.el7

The initial install did not include kernel-devel so I yum install 
kernel-devel
Still have the problem
So I downgrade the kernel - it goes to 3.10.0-327.4.4.el7
I downgrade repeatedly until I get 3.10.0-327.el7.x86_64 as that was the 
initial kernel installed.
The downgrade correctly downgrades the kernel, kernel-headers, 
kernel-tools and kernel-tools-libs BUT NOT the kernel-devel which stays 
at -327.4.5.el7
Trapped - didn't see that for a while!
So I finally yum remove kernel-devel
Then I look in yumex (with show latest - disabled) and only the 
kernel-devel for 3.10.0-327.4.5.el7 is shown. All the other kernel 
packages show the correct versions.
At this point the only installed kernel rpms are 3.10.0-327.el7.x86_64
So I explicitly ask yum to install
sudo yum install kernel-devel-3.10.0-327.el7.x86_64

so now I have
 >rpm -qa |grep kernel
kernel-tools-libs-3.10.0-327.el7.x86_64
kernel-3.10.0-327.el7.x86_64
abrt-addon-kerneloops-2.1.11-36.el7.centos.x86_64
kernel-headers-3.10.0-327.el7.x86_64
kernel-tools-3.10.0-327.el7.x86_64
kernel-devel-3.10.0-327.el7.x86_64

The virtual box command to compile and install the vbox driver is sudo 
/sbin/rcvboxdrv
which seems to have issues
sudo /sbin/rcvboxdrv

** (pkttyagent:3047): WARNING **: Unable to register authentication 
agent: GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name 
:1.6 was not provided by any .service files
Error registering authentication agent: 
GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name :1.6 was 
not provided by any .service files (g-dbus-error-quark, 2)

zero idea of what that means

a repeat of the command returns nothing
but when I run
 >sudo VBoxManage -v
WARNING: The vboxdrv kernel module is not loaded. Either there is no module
          available for the current kernel (3.10.0-327.el7.x86_64) or it 
failed to
          load. Please recompile the kernel module and install it by

            sudo /sbin/rcvboxdrv setup

          You will not be able to start VMs until this problem is fixed.
5.0.14r105127

BTW the setup param returns
Bad argument setup

At this point I have run out of ideas / patience / time and coffee.
Any ideas as to how to fix this would be appreciated.
TIA
Rob