Laptop Doesn't Sleep/Black Screen

Dell Inspiron 1545, 64-bit running Windows 7 Home.

There are other black screen threads on here but none of them were relevant to my situation really...basically sometimes when I let my laptop sleep for a long time (when I close the lid) I will look at it and its power light will be a consistent flash. This indicates it's actually not sleeping and you could also tell since the insides are working and humming.

It's only when it's completely quiet and the power light is fading in and out that it's asleep.

Now that's not really my concern. What my concern is, sometimes when it's not asleep while the lid's closed...I open it up and the screen won't show at all...why? The screen should be at least on for the whole time if it isn't sleeping.

I held down the power button to restart since that's the only thing I could think of to do. Someone please tell me of another solution to this problem...