There are several thread about PIT/Partition/ brick/ mounting problem etc.
i spent over 2 days to fix my international GT-I9300 16GB white.
i think there is not much left about PIT on not only XDA but on other websites. Which I didn't read.
some of them are scary like. don't check partition box in odin or motherboard will be dead or that's it your phone is junk/ send it to service center. blah blah blah........
but all you need to do is downgrade you boot loader..........yes.***********THAT'S IT*********
tried millions of method (yes almost million) but nothing work. and i don't want to anyone else spend that much time on it
(back on topic)
here is how i did it.
download all files at last of this post
1. Put your phone on download mod (volume down+home button+power and than volume up)
2.open odin and select option *auto reboot*re-partition*f.reset time *Nand erase all(don.t worry just do it*unless you have other option*)
3.select **GT-I9300.PIT** as pit file(DO NOT SELECT ANY OTHER ONE)
4. click start(after finishing task phone will reboot )
5.now download CF-Root for SGS3 v6.4 from here-------> http://forum.xda-developers.com/show....php?t=1695238
6. again put phone in download mode and root your phone with CF-Root (file you downloaded)
7.now put ***Restore_Bootloader_XXBLFB** ZIP file on your sd card and flash it using phone recovery (cwm)
8.now download any 3 part official firmware for your phone and flash with odin ..
method above worked for me on my SAMSUNG GALAXY S3 GT-I9300 WHITE 16 GB but i still take no responsibility
for any damage to your phone or to your Dog/cat during process.
Hope it'll work for you
sorry for my bad english.