I use the free platform theme by pagelines (latest). It's really a great theme and I would recommend it. I enabled the content widget which allows one to place widgets inside a page/post. Once I enabled it, the sub-menu options disappeared from my pages including the home page.
No Sub-menu: http://projectcloud.info/
Once this happened, I removed the content widget but the problem persisted. So I deleted the entire theme and loaded it again. The problem persisted.
Any help would be appreciated.