hdmi doesn't work

Hello

I have a dell vostro 3450. I just bought a 50" Panasonic Viera and I cannot connect the two with hdmi.

Whenever i assign the tv's input to the correct hdmi port, the laptop's screen turns black and the tv doesn't show anything. Important to say, the laptop DOES recognise the hdmi connection (it gives the sound of a new connection when I assign the correct tv port and also does the hardware removal sound when I assign the tv to another input). 

I have gone through all the obvious solutions-updated the drivers, winkey+p, fn+f1, everything. 

Thank you!