Windows Will Not Shutdown - Shutdown hangs

Dear all, I have an issue with my 7 machine, every time I hit shut down the machine will hang on the shutdown aero screen and fails to shut. If I leave it to run it loses the connection to the monitor which goes black and does not detect the PC input. I then have the hold down the button in order to shut the machine down. I have replaced the old 120 GB SSD with a larger 480 GB SSD...