This is a strange one - adding a new form doesn't work, essentially the page doesn't load properly.
I loaded up the latest GF and got this problem, then deleted and tried an earlier version but the exact same problem.
Everything else works fine plus the plugin works perfectly on other sites.
Here's a screengrab of the edit/add form page:
UPDATE: I've just updated another copy of the plugin on another different server and the same issue is happening - this time even on pre-made forms. The side panels are not loading correctly.