Macbook Pro, trouble turning on

I have a macbook pro that's just over three years old. Yesterday it took a small drop onto carpetted floor, but it caused the lid to close and open again rapidly. It then seemed (judging from the sensor light at the front and the noise of the disc running) that it was in sleep mode when opened, and active when shut. When trying to restart it or turn it back on, it never progresses to the grey screen with the apple logo, just goes straight into sleep.
Any ideas? I've made an appointment at the Mac store for Monday, but if it's a simple solution that would really save my day.

It's difficult to say. The drop may have damaged the hard drive or dislodged something internally. I don't think it will do any harm for you to open it up and reseat the memory modules and check to see if the hard drive is making a good connection to the SATA ribbon cable. If you're reluctant doing that, by all means let the Apple techs check it out for you. Ask for an estimate before allowing any repairs.