My Spanish is really bad ;-)

Pull the plug that connects your monitor to the back of your PC and put it back again.
Sometimes the contacts just stop talking to each other.

If that doesn't help, you could have a failed video section or card.

Worst case is: The monitor has failed internally, either the power supply or more likely, the high voltage section.

If you want to try troubleshooting this yourself, reply and I'll try to help you but you must have, at least, a multimeter.