It should be possible to recover, but it can take while and many attempts.
Have a look at this guide:-
You need to be in RockUSB mode first.
Double click on the remove hardware icon in your system tray.
If you are in RockUSB mode you will see the icon in the window like this:-
You MUST be in RockUSB mode to change your firmware.
To get into RockUSb mode
1) switch the player off.
2) hold down the menu key.
3)connect the USB cable
4) wait a few seconds
5) release the menu key
6) look for the RockUSB icon.
7) If you see the RockUSB icon, load the CORRECT firmware for your player using Consumerupdate program.
It this fails then as a last resort I suggest you do the Hard Reset already described to get into RockUSB mode and load the CORRECT firmware for your player using Consumerupdate program.
You will need to open your player to do the HARD reset, but only try this if you are confident with opening your player or you might break something!
You may find it easier on your player to try shorting the following 2 pins:-
These are the actual pins (posted on a Chinese website) which have also been found to need shorting to get into RockUSB mode, use tweezers or a small jeweller's screwdriver..
This would force the player into RockUSB mode upgrade mode, but you MUST look for the RockUSB icon