Black monitor after waking up from sleep

[adit]

I have Dell laptop with Ubuntu 12.04 installed. When I close the laptop lid it goes to sleep. When I open the lid, I see a black screen. I have to press some keys or move the mouse to see anything on the screen.
This is not normal. Normally as soon as opening the lid, I should see something on the screen. What is wrong?

[msammels]

As far as I was aware this is normal behaviour. When you say "I should see something on the screen", is this in Windows, or did it work like this previously in Ubuntu?

[adit]

Suppose I used firefox just before I put the laptop to sleep. When I make the laptop to wake up, I should see the firefox window. But what I see is a black screen. I have to move the mouse to see the firefox window.
The previous releases of ubuntu had no such problems. Only 12.04 has such problems.