Tadman is right with the diff idea but here's a couple more things for you.

If you're on a windows machine, I've found that sometimes rebooting the thing can make unstable code actually run -- well code that was stable and the machine wasn't. :)

The other thing to try is clear the browser cache. That has made a difference for me in the past.

Hope that helps!

There is no emoticon for what I'm feeling now.