Hi! And Thank You for a superb plugin
I issue is this:
I copied my entire website to work on my local machine so i can tweak it and make changes without disturbing the org site.
But here goes, when got the blog to work i could enter the "admin widgets menu" i have tried to dectivate all other plugins and leave display widget activated but the issue persists.
The only thing i see is text of the whole file widgets.php
As soon i deactivate it, widgets menu works fine. 
Can you reproduce this?
Or do you know why this happens?
Can it be solved?
/Thank you again
Mathias