Any thoughts as to why Windows 7 won't restart?

I have 'Windows 7 Professional' and the entire setup is completely new, my problem is that each time I need to restart the system after installing software or updates I have to shut down the computer completely and turn off the power at the wall for a couple of minutes before '7' will start again. If I don't do this and just click on 'restart' it quickly flicks through a couple of screens (probably bios and boot, they are a bit fast to read) as normal and then I just get a flashing white line about 15mm long and 40mm from the top left of my monitors. Any ideas as to how I might rectify this would be greatly appreciated as it's starting to give me the '....s'.