Here is the answer from Kreatura:
The issue is caused by an error in one of your theme’s methods (window resize function). If you open up the console you can see the js errors related to your theme. You can make sure that this problem is caused by the theme by temporary switching to a default WP theme.
Unfotuantely the error is generated by your theme so we cannot do much from our end. I’d recommend contacting the author of your theme with this case, they should be able to provide more insight and a solution for this.