Default [Q] Error when trying to unlock bootloader

Hi guys =D I'm trying to unlock my bootloader using flashtool, but everytime I try it, it shows an error message:

27/004/2014 20:04:21 - ERROR - Processing of loader.sin finished with errors.
27/004/2014 20:04:21 - ERROR -
27/004/2014 20:04:21 - INFO - Your phone bootloader cannot be officially unlocked
27/004/2014 20:04:21 - INFO - You can now unplug and restart your phone

I've arealdy rooted my phone.
I've checked if it can be unlocked (and yes, it's allowed to be unlocked)
I've installed all drivers needed.

What can I do?