Any Output Style named with the / character will not be saved. To resolve the issue, use one of the solutions listed below.
Name the Output Style without using special characters, especially the / character. Characters to avoid on the Mac include: '! @ ### $ % ^ & *. You may also want to avoid beginning a file or folder name with a hyphen, because the operating system may read that as a terminal command. On the Windows side you should avoid the following characters in your file names: ? [ ] / \ = < > : ; ' , * |.
Update to QuarkXPress 7.31 or higher.