After that I tried download mode, but it's stuck at setup connection. Any things I can still try before JIG/JTAG?
EDIT: The panic was bigger than the problem. Pulled out SIM, SD card, tried to boot it, it displayed a logo showing that there is a problem with the connection to the PC, then I booted to download mode and flashed a 4 package ROM, as it can override the boot thingy. So it's all good now.