I had the same problem with the TV not switching on straight away, it was taking longer and longer each time until it stopped coming on all together. I bought a new power supply PCB and that fixed the problem.
This is a link to the board I bought:
http://www.chsinteractive.co.uk/electrical-components/misc/le40r73bdxxeu-pcb-psu-samsung-bn44-00134a-rev1-5-3925310002ad.htm
£120 - which is just £5 more then I would have had to pay to diagnose the problem through a local repair company. It was also very easy to fit
Craig, December 2008