By hard restart, you mean pressing the power button down till it restarts.
Number one is to restart holding D. This should, i think, run a hardware test, to make sure everything is ok. Assuming everything is, I would power up the macbook, and slide in your OSX DVD, and then restart the machine again, which should allow the installation of OSX to start (Don't panic)
You shold be able to do a non destructive install of OSX, which should repair any corrupted OSX files.
Before doing a reinstall, which may not be needed at this point,
Try using Disk Utility to do a Disk Repair, as shown in this link, while booted up on your install disk.
You could have some directory corruption. Let us know what errors Disk Repair reports and if DU was able to repair them. This could just be a start in repairs and you may need a better utility to finish the job.
Then Repair Permissions.
No need to report any Permissions errors........we all get them.