So here's the deal: my sister has a Core Duo MacBook from her school (they gave it to her, but they still maintain it, kind of a lease idea) and it recently went on the fritz (applications wouldn't start up, system would hang and then wouldn't power up, etc.). Apple replaced the logic board among other parts (keyboard, top case [brown-ish due to heat; second time its been replaced]) and now its come back looking as good as new. However, certain applications will not start now after the computer's first reboot. iTunes and Microsoft Messenger are the two main culprits. Having OS X restore default preference files does nothing and neither does reinstalling iTunes. The error report always cites QuickTimeComponent.component as the culprit. Right now I'm downloading QT again to see if it will help. Ideas? Comments? Help?!