Mozilla has released a new version of the Firefox browser, version 3.6.6. This is a bug-fix update of Firefox 3.6.4, which was released last week. The new version provides a little more time for a plugin (such as Flash) to respond before deciding that the plugin has crashed. Apparently, the original version was a little too aggressive on heavily loaded systems. Further information is in the Release Notes; installation binaries for all platforms (Linux, Max OS X, and Windows) can be downloaded here.
Although it is always a good idea to keep your software reasonably current, I don’t see any reason to be in a panic to install this update unless you are experiencing plugin-related problems.