After I installed the recent security update for Mac OS X v10.6.2 Snow Leopard on my MacBook Pro, I noticed this problem just today. The problem affects all multi-touch gestures, including but not limited to the following:
Gestures Not Working
3 finger swipe
4 finger swipe (switching applications, show deskop, and expose')
Rotate & Pinch
Gestures Working for now
Secondary click (on bottom-right of trackpad)
2 finger right-click
2 finger scrolling
Tap to click
Click
Dragging (without enabling "tap to click")
I've had my MacBook Pro since December 2009 when I bought it at a Best Buy, and I have a Best Buy warranty so if it is hardware-related, then I can just drop it off at a local Best Buy and let a Geek Squad Agent deal with it.
If you want to send your complaints to Apple about this issue, send an email using this link (product-security@apple.com). According to AppleInsider.com, the public release of Mac OS X v10.6.3 Snow Leopard is expected to be released in 6 weeks from now with more support for certain technologies, applications, and more stability to target crashes, bugs, etc.
THINK DIFFERENTLY