Karen Stoll, first try what Apple suggest (not including step 14;-):"
The computer will not power on
1. Remove any connected peripherals.
2. Try known-good power outlet.
3. Try known-good power adapter and power cord.
4. Remove battery.
5. Press Caps Lock key to see if light on key comes on. If it does, hold power button
down for six seconds to shut down the computer and restart.
6. Reset the power manager by pressing the key combination Control-Option-Shiftpower.
Warning: Make sure you do not hold down the "fn" key when resetting the
Warning: Resetting the power manager means you will also need to reset the
date and time (using the Date & Time control panel).
7. Reset PRAM (Press the power button, then hold down the Option-Command-P-R
keys until you hear the startup chime at least one additional time after the initial
8. Disconnect keyboard completely. Inspect connectors. Restart with keyboard
9. Remove any additional RAM.
The AirPort Extreme/Bluetooth card has specific handling precautions.
Make sure you review the section "AirPort Extreme/Bluetooth Card" in the Take Apart
chapter before continuing.
Remove AirPort Extreme/Bluetooth card.
11. Try known-good DC board.
12. Verify cable connections and check cables for damage.
13. Verify power button is connected properly to logic board, if power button is not
functioning correctly or damaged, replace the top case.
14. Replace logic board.