Not Letting me "Save" Changes to my Menus

I have added new menus and submenus, but when I try to put the pages under the correct menu, it wont let me save it. Very frustrating. I contacted my hosting company and they increased my storage and number of pages to unlimited. Not sure what to do… When I hit save the screen always says:

Most likely causes:
•The website is under maintenance.
•The website has a programming error.