LG Flatron turns off when it is connected to my pc

Hey, I have an LG Flatron W2442PA and a week ago it didn't turn on in the morning. When I turn it on, the button lights up for a few second and then turns off again without anything happening. Only when I unplug it for 30 seconds+ and plug it in again it turns on for a few seconds before turning off again. After about 10 tries it usually stays on for the day until I turn it off or it changes to standby. This only happens when it's connected to my pc via HDMI or DVI and happens with 2 power cables that I tested on other devices. So its not the power cable, neither the HDMI / DVI Cable as it happens with every combination of these cables.