One of our production pages stopped working properly. Tracked it down to the fact that one of the dependencies does not exist anymore:
http://google-maps-utility-library-v3.googlecode.com/svn/trunk/infobox/src/infobox.js
This URL is used in most of the example codes that were the basis of the webpage.
This is probably easily solved but a quick google showed no one has noticed this, I think it has happened in the last hour and just wanted to put the information out there in case people are panicking.
It seems that the library is being moved to Github (it seems the infobox.js wasn't moved yet), see the announcement on main page: https://code.google.com/p/google-maps-utility-library-v3/ But still, the problem with your code is that it's not a good practise to reference code from code.google.com svn repository. It's like referencing a code from Github, it can be changed/moved/removed any time. You should either download the code and include it in your project as .js file or host it yourself on some CDN server.
UPDATE
The google utility library (including infobox) is hosted here on github now. As said before, it's not mean to be referenced from there in projects.