Hi,

I have a flat screen LCD TV, Philips 50PF7321D

When it is on there is normally a green light indicator in the bottom left of the unit ( not the screen). It is now just over 1 year old and a while ago it started having problems. When switching on the sound comes on immediately but the picture takes a long time ( 2-3 mins) to appear. Now, when it is switched on the green light goes out after about 20 seconds ( the screen is blank at this time) then the light flahes red on and off and no picture will appear.

If you unlug it from the electrical supply and then reconnect will eventually, after several attempts, cause the green light to stay on and a picture will appear.

Anyone know what causes this and how it can be cured?

Unfortunately, you are not the first to have this problem. There are a few websites where others have expressed similar concerns.
I have had the same issue and it has only gotten progressively worse... now have to unplug and plug it in well over 20 times before picture will come on.
Hope you are able to get some answers that help. I have yet to find any information on it.
Phillips / Magnavox LCD TV Complaints - WARNING: Do not buy a Phillips/Magnavox product!