I have a Samsung LE32R74BDX LCD tv, 'have had it since late May. It's been replaced (by Selfridges) twice. I'm now on my third set. I also have the same problem, it only occurs when I use my HP notebook PC which connects to my DG834G Router.
The fact that I have been more or less testing this theory for around 3 months, I'm sure I can conjecture that there is some harmless interference between my laptop and the TV. The interference may also be compounded by the fact I also have an integrated Bluetooth module in my notebook.
THIS ONLY HAPPENS WHEN I USE MY NOTEOOK PC, OTHERWISE THERE IS NO FLASHING POWER INDICATOR LIGHT. My wife has a DELL notebook pc with WiFi but there is no interference. She doesn't have Bluetooth in her notebook........
From what I've read in other posts in various forums there is certainly some correlation to the wifi and notebook and the R7 LCD TV.
I want to add that this doesn't affect the TV in any way and I am otherwise very happy with it - highly recommend it!