hi guys,
I asked this before when it happened to me but I could never make it work.  So I bricked my unit today trying to flash a build of switchfin with Asterisk 1.6.  I posted about it over on the other thread but basically there seems to be some incompatibility between the G729 "hack" and v1.6 -- it works ok w/ 1.4 but 1.6 does not load and causes you to get locked out of the GUI as well with no asterisk running.

I was not excited to have to disassemble my ip02 again and attach serial console, stretch cat5 cables across the room etc etc to flash it with uBoot.  So I was determined to figure out if I can debrick it without -- because I could still ping the unit and actually I could still SSH into it (dropbear is running).

anyway I knew the basic steps:
-place the uImage into /persistent/imageupdate
-flash the image
-reboot the unit

but I keep failing MD5 checksum when I did this (I checked in the "/persistent/imageupdate/flashresults" file)  I was using FTP (binary mode) to transfer the uImage.  I guess this was somehow the problem because the image is getting corrupted somehow during transfer.  So I want to use TFTP instead but I do not know the syntax.  So I dig through the switchfin-GUI source files

$cd switchfin

$find . -name *update.html

./dl/asterisk-gui-4.0/config/flashupdate.html

inside contained the proper syntax! (thanks Jason)

tftp -g -r uImage-md5 192.168.1.10

(substitute 192.168.1.10 for the actual IP of your TFTP server hosting the uImage-md5 file)

now, here is the full procedure:

1) build new uImage-md5
2) place on tftp server
3) ssh into IP0x and execute these commands

cd /persistent/imageupdate

echo 3 > /proc/sys/vm/drop_caches

tftp -g -r uImage-md5 192.168.1.10

flashupdate file ./uImage-md5

... wait -- cross fingers, and if successful ...

reboot

I hope this might help somebody else who might get into the same situation.
cheers