Which unlocker did you use? Are you sure it was for the X7510, not the X7500 or X7501? Can you post a link for us?
This is the correct version for the X7510.
All may not be lost, however it looks! Can you access the Bootloader mode (tri-colour screen)? This is accessed by pressing the Camera button (all the way in) while pressing the reset until the bootloader screen comes up.
From there you may be able to connect via USB which should then allow you to either flash the ROM, or reflash the HardSPL. If you still can't get a connection, you may be able to flash using a MiniSD card.