well thier might be a problem with soem of the wires inside ur machine generaly the only time u should get a no signal if everything is working properly is when u shut down u might of enabled a option to turn of hard disks etc that might also be a cause but other than these geuses i have no idea an opton would be to open upur comp check all the wires are secure and yjen if thats not the problem u might want to try reinstalling....