Hey man, i had the same problem for like 5 hours! you can still boot into the download mode if you're fast enough and from there just flash it again with a decent rom and make sure you've ended all kies processes in ctrl+shift+esc. Although I have a new problem if people wouldn't mind helping me, all of the roms i try loading now, with the exception of one i don't want as adriod market doesn't work and it's german or something, get stuck at that animated S on boot up. They seem to instal fine but after that they don't progress an further. TBH i just wann go back to kies, too much effort has been spent today and my gps doesn't work still. If anyone can help me get back to using kies with a stock build again, i would be greatful. thanks.