I've bought a GT-I9100G, flashed it with an original I9100 rom and the phone was bricked by the wrong firmware. After that, I couldn't flash it with the right firmware neither.
I have spent a whole day to figure out the problem and I have found a guy, who had the same problem earlier.
He told me what to do:
Warning! Use this description at your own risk! I can't guarantee that your phone will be alright. If you are brave, just give it a shot.
1. Download the required files:
-In case of the blocked file servers, the pit has been uploaded to a reliable Hungarian site-
TI OMAP 4 .PIT FILE:
PIT for I9100G Samsung Galaxy S 2 II
HOW TO DOWNLOAD FROM DATA.HU:
The stock ROM:
Go to http://www.sammobile.com/ and find a rom for your device (rembember, you have to look for I9100G firmwares not for I9100 ones)
2. Repartition with Odin
Turn off your phone and remove the battery.
Put it back and Press these buttons in this order:
Volume Down + Home (Menu) + Power Button
After that, you will see this:
Now, press the Volume Up button.
Your phone is in Download Mode now.
Connect your phone in this mode to your PC. It will install a few drivers, just wait patiently.
After the installation, you have to see this:
Now, browse the downloaded .PIT file to its place.
Check the re-partition box and press START.
When it finished, detach your phone.
3. Flash the new Firmware
Browse the downloaded firmware to the PDA section in Odin.
DO NOT CHECK THE RE-PARTITON BOX THIS TIME!
Hit the flash button and wait patiently.
When it finishes just enjoy your SGS II!
If you don't understand something, just ask in the thread or send me a private message.
I'll write some keywords here, so Google can find this thread easier:
I9100G flashed with I9100 firmware, bad flashing, bad flashed I9100G, bricked I9100G, dead I9100G, I9100G PIT, .PIT, *.PIT, pit file