I've got a WP 3.4.2 site running on a HostGator server using a theme called Blogolife. Everything's working fine, except that the facility to use a custom menu is broken. If I go into Appearance > Menus and create a named menu, with any content (pages, custom links, both or neither), Save it, then select the menu in Theme Locations and hit Save, the entire menu disappears from the site. If I select the blank (default) menu and hit Save, the menu returns.
I thought this might be a theme issue, but I used Live Preview with Twenty Eleven and selected my named menu, and the menu went away there too!
What could be going wrong? Could it be something on the server side? (Bad file or directory permissions, something like that?)