Let's try to rule out all other options.
So, nothing happens when you press the Power button.
1. Obviously, check the lock switch (You would be surprised to see how many people forget that!)
2. Remove and reinsert the battery
3. Press the reset hole
4. Press HARD on the battery cover and press the Power button (Could be a stupid battery error)
Basically, what happened was the bootloader somehow, to put it bluntly, crapped up. If you can find a x51v bootloader, you would probably be good. I do not believe to have a x51v bootloader in my files, offline or online. I will have to check with the all awesome LennySh to see if he has something for you.
I cannot give a straight-out answer to say if it is dead or not. From my experience, I'm 80% sure it's totally dead. Seems kinda strange it killed itself on a Lenny flash. Those don't tend to happen offen.