You may be experiencing HDCP issues and what you might want to try is doing what R. Proffitt suggests and if that does not resolve the issue, you may have to play around with the connection, powering off sequences. Whatever you attempt doing, never hot plug your cables (i.e. disconnecting or connecting them while your devices are powered on). HDMI cables carry a low DC voltage and hot plugging them will damage your equipment!
The recommended power-on sequence is to wait about 10 seconds after turning one device on before turning the other. This allows the HDCP handshake renegotiation to take place. Ideally, you should not have to turn the device you're pushing the content from, but that may not be practical. If you switch inputs, you should also have to wait 10 seconds to allow for the timing of this renegotiation to take place. Make sure that all your cables are securely attached.
So to recap everything follow this sequence:
Power off all your equipment (unplug from the wall socket)
Make sure all the HDMI cables are connected securely.
Power on the LG TV
Then 10 seconds later, power on the source device.
You may have to reverse the last 2 steps because some devices work better in negotiating the HDCP handshake when the source device is turned on first.
Hopefully this solves your issue! Good luck!...IFV