Here's a dumb question, if as it seems from what you wrote the drivers BOTH stopped working while you were away and were NOT using the machine, have you tried pulling them out, and going over them and the interface board to ensure a bug hasn't died and shorted something?
If they just suddenly died while not being used, then it's usually got to be one of three things from my experience:
1 - you left the power connected and had a surge or strike that hit components
2 - there is or was moisture in the system, or damage from moisture/condensation
3 - a critter died on components, or left waste on components, shorting them
cheers,
Ian
It's rumoured that everytime someone buys a TB6560 based board, an engineer cries!