GTDInbox relies on a key piece of information in Gmail's internals for some of its more advanced functionality, such as creating/renaming labels (at your request). Occassionally, this piece of information will move and GTDInbox will lose some functionality.
GTDInbox can find the information it requires, but it's an intensive process. So we left it for you to decide when you run it. It may take several minutes, but it is completely harmless. To begin, please click 'Fix Gmail AJAX' below.