Can you confirm that you are fully updated? (Theme and Plugins)
You can find the latest version numbers here: (http://theme.co/changelog/) Then you can compare them to what's installed on your site.
If you find anything to be out of date, you can review our update guide.
You could also try testing for a plugin conflict. You can do this by deactivating all third party plugins, and seeing if the problem remains. If it's fixed, you'll know a plugin caused the problem, and you can narrow down which one by reactivating them one at a time.
Let us know how it goes!