I use a Toshiba Portege laptop. I also have an LG W2452V monitor hooked up via HDMI. The notebook lid is normally closed and I only use the monitor.
Today the monitor refuses to show anything. However it seems as if it has signal.
Some tests I did:
If i unplug the HDMI cable I can hear the Windows "device disconnected sound". The monitor displays the "No signal" message and the LED turns yellow. When I plug the cable again I hear the "device connected sound" from Windows, the "No signal" message is removed from the monitor, the monitor LED turns blue, the whole screen lights up as if it's going to display something and then nothing...
Same behavior if I use the special laptop button that shifts through the available signal modes. E.g. if I pick "laptop LCD only" the monitor shuts down. If I pick the HDMI or HDMI/LaptopMonitor the monitor shows the above signs but it doesn't show anything.
Using the "Extend desktop to second monitor" has the same results. The mouse cursor can move to the monitor but nothing is displayed...