Blackberry Torch - white screen?

If it's a software malfunction, a reset or removing the battery ought to clear it up. Otherwise, the circuitry's likely fried and will require repair or replacement - recommended if warranty still applies. I have one like that which is just a tad fickle, with some gentle presses & turning screen on-off it can go from blank to responsive, so I didn't bother with a repair which was ~60 / 80% the cost of the device, new.