Gently press (don't hold) the power button once.

I'd like to know if you ever got yours out of sleep mode? Mine wont wake no matter what I do to it.

I'd really like to know if you fixed this too. Mine won't awaken from sleep anymore either. Doesn't matter what I try.

It turned out to be a bad Motherboard. Dell replaced it under warranty.

Try this test, if you boot your computer press the power button once while it's booting. If it does the trick of standby but not full standby its probably a bad motherboard.