Unplug one end of all HDMI cables.
Remove power to the TV for 10+ minutes. Plug the TV in and only attach the HDMI from the BD player. Re-test.
If this fails, you'll call service.
Having found this forum through Google, I am no contributer, I'm just here to hopefully find someone knowledgable enough to help me out. So here goes:
My
LG 42LA6208 3D Smart TV, and
LG BP430 Blu-Ray 3D player
Connected to HDMI
Have worked fine together for 2,5 years.
No suddenly the connection is lost.
When the Blu-Ray starts up the usual screen is shown on TV.
But after a few seconds the screen flashes to black.
This happens a few times.
The flashes are not regular, and not all the same length in duration.
This continues for a second or 10 to 20 maximum, and then the TV shows a disconnection message like "no signal for current source, check the status of external source". This is different from the message when the cable is disconnected, the TV detects this and then states that the cable is disconnected.
The TV has two HDMI ports I can use. Both have the same result.
I have tried with tree different HDMI cables, of which one was expensive, gold plated.
Although I do not have another identical Blu-Ray player, I have tried other devices on these two ports: a DVD player, and a digital set-top box. Both work excellently on those ports. For those connections I used the same cables I use for connecting the Blu-Ray.
I have taken the Blu-Ray to other peoples TV's.
Both of those TV's take my Blu-Ray without so much as a stutter, excellent results. One of those TV's was also an LG, but I did not note the model, a different one from mine though.
I have updated both devices' software to the latest, and did a factory reset on both.
All of the above lead to no result.
I am at wits end, since the Blu-Ray seems fine because it works with other TV's, but the TV seems fine also, since it works fine with other devices. Both worked together fine for 2,5 years.
Does anyone here have any idea how to proceed?

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic