[Galaxy S III Q&A, Help & Troubleshooting] Bananafische:
Hi - I tried posting this in Development where I thought it should go but I haven't posted at all before so it won't let me.

I've gotten myself into a very messy (and probably stupid) situation with firmware with my I9300 - there's a very real chance I think that it is non-recoverable, but if anyone could give me some advice on what else to try I would be extremely grateful!

My problem:

Galaxy S3 I9300 16gb international won't boot - stuck at Device Name screen.

Won't boot into recovery

Will boot into download mode

Odin connects to device, but trying to flash stock ROM freezes at 'NAND Write Start!' or just FCs ("Odin has stopped working" reported by Windows

Heimdall won't recognise my device (does it even work with the s3? I don't know) so I can't print a PIT or anything

How I got here (over about 4 weeks):

Started with I9300 16gb international version (Grey import from Hong Kong to Australia, booted in French but let me change to English)

Gained root access through CWM touch kernel and Odin

Flashed AOKP Milestone 6 ROM

Used 'Secure Settings' (app) and 'Locale' (app) to set up a lockscreen PIN that enabled and disabled dynamically according to location rules (worked pretty well!)

Decided I wanted to encrypt my device

Clicked through all warnings, followed instructions to set PIN (didn't disable Secure Settings, the app that allowed the lockscreen changes outlined above)

Encryption successful, booted successfully using the PIN set

Lockscreen goes funny - 'quick PIN' option in AOKP (where you don't have to press OK after entering the PIN correctly) stops working

Any PIN at all at this point will unlock my device

Reboot to discover that my original encryption PIN has stopped working

Seriously, I tried it like 20 times including slight variations in case I mistyped, and other PINs that I use in case I misremembered

Rebooted into CWM to try to flash a new ROM

Can't access internal SD due to encryption

Use Galaxy S3 Toolkit to 'download and flash new stock rom, kernel using Odin'

Didn't know which firmware to download so i went with option 5 (GT-I9300_BTU_I9300XXALF2_I9300OXAALF2_I9300XXLF2)

Odin connects sucessfully, flashes device

Device reboots into 'Trouble with firmware upgrade - connect to samsung kies to fix' (or whatever it says)

Download and install Kies (i had the USB drivers for the phone installed previously)

Kies won't recognise my phone on any level for emergency recovery

Decide that the internal SD card encryption is causing the problems, and that maybe I need to repartition

Don't notice all the warnings about repartitioning

Download PIT files for I9300 from somewhere

Try reflashing ROM using one of these PITs (I didn't know any better so I just used GT-I9300_mx_20120329.pit, which in retrospect is probably for a device with different internal storage size)

Phone stopped giving me 'Firmware update problem' screen and started going to the 'GT I9300' booting screen, but never got past that point

Repeat ad infinitum - I've tried flashing several different stock ROMs, using several PITs and am now at the point mentioned above.

Only other information I have really is that on the back cover behind the battery it says 'Model GT-I9300' and 'SSN-I9300GSMH' if those are important.

Other forums seem to indicate that I have a NAND read/write issue, but trying to flash a stock kernel (which was the advice given) results in... 'NAND write start!' freeze :\

Like I said, I have no idea if this is recoverable in any way at this point, but if anyone has any ideas I'd love to hear them!

Thanks