Toshiba Satellite C660D-101 Won't open/Black screen Sometimes.

Hi,
I have a Toshiba satellite which sometimes (most of the times) when I power it on it won't start, sometimes it starts normally (mostly the day after!).
When it doesn't start the power led is on and the fan is working. Also no signal on the VGA port.
I tried the 1-2 min pressing of the power button with power & battery removed, nothing!
I also opened it, cleaned the fan and replaced the thermal compound (paste) from the processor, still nothing!
Any suggestions?

Thanks in advance!