It isn't the first time an update to MacOS X breaks something. The major problem is that sometimes they don't even bother releasing a fix!
I use Tiger and over three months ago there was a security update that broke my network settings pane. Immediately many people started complaining in Apple support forums and two weeks later there was a new security update, but the issue wasn't fixed. As of today, it wasn't fixed yet, althout there are workarounds to be able to change your network settings.
This is one of the reasons why I now have Ubuntu on my macbook (dual boot).