HP Elitebook 850 Black screen after sleep mode

Hi,

I've got an HP Elitebook 850 which is about 3 weeks old. It's running Windows 8.1 with most of the HP softwares, available for this model, installed.

Once the laptop goes into sleep mode you can't wake it up for some reason. The screen remains black and all LED light seem normal. Only thing to do is either ctr+alt+del to reboot or forced shutdown using the power button.

Any ideas?

Best regards