Acronis 2012 hangs at loading screen using bootable media, HPZ620 on Win 7 64bit

Hi All, I have been using Acronis 2012 bootable media sucessfuly for 6 months on a handful of Dell desktops and servers and had no problems however the company i work for have just bought in a load of HP Z620 desktop computers running Windows 7 64 bit.

These HP PC's seem to have trouble loading Acronis 2012 from bootable media, i.e. the option screen shows up and prompts me to press "1" to load Acronis or "C" to continue to Windows. When i press "1" to load Acronis the message appears in the top left of the screen "Acronis loading, please wait" and the program hangs on this screen and does not advance even after being left for an hour.

I have seached the forums for answers on this and have tried experimenting with different startup parameters such as "acpi=off" and "noapic" with no luck. I have also followed up on a suggestion to download the latest bootable media .iso through my web account but this still causes Acronis to hang when loading.

I have also tried using both a USB memory stick and writable DVD to run the bootable media but no joy there.

The HP Z620's have a startup option which allows you to run a UEFI application from bootable media manualy. This results in the machine displaying "Starting Acronis Loader" which is promptly followed by an EFI runtime error "21495809".

Any suggestions in resolving this would be much appreciated.

Pete