Last night I put my computer to sleep as I always do before I go to bed. Today when I got home from work I went to wake up my computer and all the lights, fans, keyboard and mouse started up, however I was left with a blank screen. So I turned the computer off and on and still nothing. I plugged my cable box into the monitor and it works fine so I know that's not the issue. I can hear the computer start up through the speakers, there's no beeps that would indicate a problem with the processor or graphics card, and I can type in my password to log in to the computer. The monitor says no signal detected. Any ideas as to what the issue could be?