Unable to update BIOS on Z420 Workstation

Hello,

I'm having an issue with updating the BIOS on a Z420 Workstation. Product number LJ449AV.

The current BIOS version is 1.02 03/09/2012 and the latest BIOS version is 3.88 05/26/2015. I am downloading the latest BIOS version, in the file sp71579.exe, from here: http://h20565.www2.hp.com/hpsc/swd/public/detail?sp4ts.oid=5228608&swItemId=wk_149656_1&swEnvOid=4059#tab1

When I attempt to use the HPQ Flash utility to update the BIOS, a message appears at the end of the Flashing new BIOS step stating An unrecoverable error has occured while flashing the BIOS. Error code = 0x0D (Unknown error code).Here is a copy of the HPQFlash.log file:

07/30/2015 09:41:04.228  
07/30/2015 09:41:04.229  --- START NEW HPQFLASH SESSION, HPQFLASH version 4.40.1.1 ---
07/30/2015 09:41:04.231  Command line = 
07/30/2015 09:41:06.752  System name = HP Z420 WORKSTATION
07/30/2015 09:41:06.753  System ID = 0x1589
07/30/2015 09:41:06.754  System Serial Number = 2UA22509HT
07/30/2015 09:41:06.756  AT-p supported = 0 (0:  not supported, 1 supported)
07/30/2015 09:41:06.757  Version of BIOS in system:
07/30/2015 09:41:06.758     Family = J61
07/30/2015 09:41:06.759     Major version = 0x1, Minor Version = 0x02
07/30/2015 09:41:06.761     Release Date = 03/09/2012
07/30/2015 09:41:08.034  The binary to create HP_TOOLS partition is not present: 'C:\SWSETUP\SP71579\HPQFlash\Installer.exe'
07/30/2015 09:41:08.096  Version of BIOS in ROM update (in CAB file):
07/30/2015 09:41:08.098     Family = J61
07/30/2015 09:41:08.099     Version = 3.88
07/30/2015 09:41:08.100     Release Date = 05/26/2015
07/30/2015 09:41:56.806  Don't need to Backup BIOS files.  Either system is not a laptop or BIOS does not support backup from USB device.
07/30/2015 09:41:57.809  ***** Start FLASHING *****
07/30/2015 09:41:57.833  Start Saving Original BIOS Contents
07/30/2015 09:45:40.720  End Saving Original BIOS Contents
07/30/2015 09:45:40.723  Start flashing (Write)  Attempt #1
07/30/2015 09:45:40.724  Start Flash Rom Image (Write)
07/30/2015 09:46:41.003  End Flash Rom Image (Write), bStatus = 0
07/30/2015 09:46:41.006  End flashing (Write)  Attempt #1
07/30/2015 09:46:41.008  ***** END FLASHING PROCESS *****
07/30/2015 09:47:39.207  Exit hpqFlash:  Return Code = 0xd
07/30/2015 09:47:39.209  --- END HPQFLASH SESSION ---

When I attempt to boot from a USB drive and use the DOS Flash utility, the following is displayed on the screen:

Transferring System ROM... 100%
Verifying System ROM...

Error! System ROM is invalid.

I have tried downloading sp71579.exe using two different computers on different Internet connections using different web browsers, but the same issues occur. I have also tried disabling the antivirus but that didn't help either.

Thank you for any help you can provide!