Hi pepedog.
I can't SSH at all anymore, I've only got serial access now, so I can't perform any such commands.
So I actually went ahead and TFTP'd in the ramdisk, based on the instructions at 
viewtopic.php?t=1323. Rebooted the PPV3, and it didn't help—was still stuck forever on a flashing front LED.
So then, I went and followed the entire guide at 
viewtopic.php?t=1323, substituting the references to ce_kernel_redstone_v63.img and ce_ramdisk_v2.0b.img with ce_pogopro_kernel_r9 and ce_pogopro_ramdisk_r9 respectively.
When trying to write to NAND, I was getting a failure with the error:
nand_write_ecc: not page aligned data
I discovered that the sizes of the images are not multiples of 512, so I rounded them up, and this then worked.
All seemed to go okay. But now, when booting up the PPV3, I get no LED on the front whatsoever.
Here's the serial output I'm now getting:
$this->bbcode_second_pass_quote('', 'S')tage-1 Bootloader XCE_STAGE1: 1.1: Tue Feb  8 01:40:26 PST 2011
Attempting to set PLLA to 700MHz ...
  plla_ctrl0 : 0x0000000A
  plla_ctrl1 : 0x000E0000
  plla_ctrl2 : 0x001C01A0
  plla_ctrl3 : 0x00000016
PLLA Set
Setup memory, testing
Reading NAND, Image 0
  Hdr len: 0x0001C030
  Hdr CRC: 0x39F6D832
 OK
U-Boot 1.1.2 (Jul 29 2010 - 19:36:07)
U-Boot code: 60D00000 -> 60D1C030  BSS: -> 60D21800
RAM Configuration:
        Bank #0: 60000000 128 MB
SRAM Configuration:
        64KB at 0x50000000
NAND:128 MiB
In:    serial
Out:   serial
Err:   serial
Setting Linux mem= boot arg value
Hit any key to stop autoboot:  0
NAND read: device 0 offset 0x100000, size 0x300000
data abort
pc : [<60d0d61c>]    lr : [<60d0cde4>]
sp : 60cbf470  ip : 00000000  fp : 60d1ea5c
r10: 00000100  r9 : 00000003  r8 : 60cbffdc
r7 : 00000007  r6 : 60cbf527  r5 : 000000ff  r4 : 00000000
r3 : 00000000  r2 : 60cbf524  r1 : 00a00000  r0 : 00000000
Flags: nzCv  IRQs off  FIQs off  Mode SVC_32
Resetting CPU ...
...and it just keeps forever resetting and doing the same thing.
Anyone got any suggestions? Thanks again for your help guys.