I have a 15" Powerbook with 1.5 gigs of ram. It's the latest revision model. Up until now, it has been working flawlessly. But on Friday, while burning a data dvd, it started lagging up on me. Even after a restart, things were lagging up while trying to open. Periodically since then, things have been running slower and I've been getting the beach-ball in everything from Safari to Preview to Mail to iPhoto to Photoshop. I'm wondering if there's anything I can reset, clear, or etc, to get this thing out of the funk and back to running smoothly? Thanks.