Can't update bootloader

I have a system with bootloader 10/17/2006 and want to update to bootloader 07/02/09.

I've done this a number of times on other systems, but get the following error on one I tried today.

[vxKernel] -> sysBootImagePut 0,"/ramdrv/bootrom_070209_SD2.bin"
Reading bootrom image:
 /ramdrv/bootrom_070209_SD2.bin
0xec694 bytes to read..............................
Flash image does not contain a board ID cookie!
The file may not contain a valid bootloader image!
Do not proceed unless directed by Acme Packet support!
Do you want to proceed (y,n)?
n

Exiting.
value = -1 = 0xffffffff = wrs_kernel_bss_end + 0xfdaee39f

 

Ideas?