Hard Drive not showing up

I have the 750 GB My Passport that I’m using with a Macbook pro. USB 3.0. 

I’ve had it for about a month and it worked great. Today I shut my macbook with the drive still in it as I’ve done many times before. When I came back and got on my computer again the drive wasn’t showing up anywhere. So I unplugged it and plugged it back in. Nothing. It’s like there is nothing plugged into my USB port. And the small light on the drive is lit up but not blinking. It usually blink when it is plugged in. I also noticed that when I plug it in the drive makes kind of a strange noise. It’s very quiet but I don’t think it made the noise before when it was working properly.  I know my USB ports work because I was able to sync my iPod with no problem but I haven’t gotten a chance yet to try out the drive on a different computer. 

Any ideas?

Hello, I am using a MacBook Pro with a cinema screen attached.  I, too, have closed my macbook to use in clamshell mode and it does not show up the next time I use my computer.  If anyone has any info, it would be appreciated.  Thank You,