have a look at your power supply board...
I had very similar symptoms to yours, and also originally thought it was likely a failed inverter board, but it turned out to be bad capacitors on the power supply board (which apparently is a widespread issue affecting many models of Samsung TV. You can find lots of info if you search avsforum.com for "Samsung capacitors") I managed to fix mine for about $10. see my play by play here: http://forums.cnet.com/5208-13973_102-0.html?threadID=359389
So I'd suggest you grab your Philips screwdriver and take the back off the set, and have a look at the power supply to see if you might be able to fix your problem at low cost.
To remove back, I put the TV face down on a blanket then removed all screws around the perimeter of the case, and one screw next to the AV connections, then lifted the back of the case straight up. I think you can remove the back of the case without laying it down if it is on it's stand, but mine was hanging on the wall w/o stand so that wasn't an option. Then there is another metal mesh cover that has to come off to see the power supply board and check out the capacitors. Definitely worth the time to have a look yourself if only to help diagnose the problem. If it IS the capacitors, you could fix it yourself, or take just the power supply board to any electronics repair place for a quick and low cost fix vs. getting a Samsung tech to visit your house.
One post I found useful with photos and good description is here: