Sorry about this change, but it was intended actually. We had some issues with wrong guild being fetched when for example one guild is called "original" and the other is called "öriginal" so we're now searching for binary match of your request.
We might change back to case-insensitive search soon tho, it's just that there's a lot of preparation for cataclysm changes going on at the moment and we're forced to focus on that.