i had this problem and discovered that this is a well known problem to samsung so they have increased thier guarantee to 5 years in respect of this problem only. i found this link which will solve the problem if your unit is under 5 years old yhttp://www.bbc.co.uk/consumer/tv_and_radio/watchdog/reports/consumer_goods/consumer_20080407.shtml
if you have a problem with this link try this uk no. 0800 988 0123
lisa, August 2008
