Manuel,
You're running into a minor bug in our latest release. To fix, you would need to follow the directions in
this post
.
The issue only occurs when you're trying to filter the usermap area by a specific social network. That happens if you use the drop-down or click one of the icons on the main overview page. Once the error happens, you need to logout and back in again to 'reset' the view.. and then don't filter that way.
It's a small issue (in the scheme of things), but are likely going to put together a small bug-fix release later this week or early next with this and a few other minor things. That will hold everything over until the next major release, due in February.
I hope that helps,
Alex