I was trying to flash the rom on my Galaxy Ace 2 from Jellybean (which makes it slow) back to Gingerbread using Odin 3. I have done this sort of flashing a few times without problem, however this time my PC decided to crash halfway through for some reason I have no idea why its normally very stable.
Anyway result was phone would boot loop and no recover mode available just download mode and no matter how many times I rerun the flash and even though Odin3 said it had all gone fine it still did the same (note the rom I was using I had used before ok)
In desperation and because phone is not worth a lot I even use Nand Erase All despite everyone shouting DON'T DO IT on here you WILL brick it
BUT I now have it up and running again using a rom from here
Note as I haven't posted more than 10 posts so can't add a proper link so copy and paste this then change hxxp to http
Flashed with Odin in download mode and OMG my phone now works and as I have read that many people have phones bricked like this or have been as crazy as me and used Nand Erase All I though I would share this good news. Just to note as well although I'm sure it has no barring on the process as it didn't change what the phone was doing but I left battery out all night before doing this but thought I would mention it just in case.
I used first rom on list being from the UK but (note if you reading this in a few months or years from now it may not be the same one I used)
There is rom for what looks like all Samsung devices in many different languages.
Please note I am not an expert just lucky amature
Hope this helps