Indexhibit Support

Hi,
I've got my Tumblr blog all nice and nested into my Indexhibit site except for the scrolling behavior. Check it here:
blioux.com/info/journal/

Of course you can scroll with your mouse wheel but not the right side scroll bar. Works fine on mobile devices as well.
What can I change in the code to make it scrollable with the side bar?
Thanks for your help everyone!

What's really strange is that it only behaves this way if the screen is maximized. If you minimize ans then maximize it will behave normally.