Hi, I bought an Aluminum MacBook (base model [2.0 GHz] with upgraded 250 GB HDD) in mid-November. After about a week of use, I somehow lost the ability to use the three-finger left swipe on my trackpad (used to navigate "back" in Safari, previous photo in iPhoto, etc.) in some programs. For example, it doesn't work in iPhoto or Safari, but works to go back to the previous folder in Finder. Oddly enough, all other gestures on the trackpad work perfectly in all programs--including Pinch-to-Zoom, two-finger right click, two-finger scroll, the four finger Expose feature, and the three-finger forward swipe. I have tried updating my trackpad via Trackpad Firmware Update (which doesn't work, as it's already updated to the latest version) and don't have anything like Multi-Clutch installed. What should I do?