Green lights appear in the middle of the night while on standby?

I have a Toshiba 17WLT56B wall mounted TV in the bedroom.
The TV works fine, no problem. When switched on one green led is displayed. When on standby this replaced by one red led
After watching tv in the evening in bed we switch the tv off and it goes to standby with one red led.
Periodically about 3am the red light is replaced by 'two' green led's. These remain on until the power is turned off at the wall.
All then works fine until possibly the next night or even a month later when the same thing happens again.
There is nothing in the manual about this problem.
Any ideas, solutions?.