RN516 not booting after powercut.

Hey guys! 

Hopefully someone can save me & help fix my ReadyNAS!

OK, so here goes.  Woke up to a powercut this morning, sorted out that issue, but when i went to reboot the RN516 i was greeted by an error message on the screen, "mount_block_root +25e".  I have attempted to access the boot menu by holding the reset button whilst turning the unit on but this message is displayed before the boot menu can be accessed, I have removed all the HDD & attempted to access the boot menu again with no success.

I then thought to create a recovery usb, downloaded the recovery tool & followed the instructions, formatted the drive ok, however when i reach the part to select a firmware image there is nothing in the drop down menu to select & when i select "create" an error log is created, i'm guessing because there is no firmware version selected? So now i am unable to create a recovery drive! 

Has anyone else encountered this error & or these issues? Any help would be appreciated, i've just lost 1000 films! Thanks in advance.