Content Query Web Part Key cannot be null

Content Query Web Part Key cannot be null

ArgumentNullException: Key cannot be null.
Parameter name: key

Very useful error message!!!! There is a conflict with the Developer Feature in SharePoint 2013 which appears to break the content query web part. Not so hot if you are relying on using this web part on your development site where you need the development feature to be available.

To resolve this issue you will need to disable the feature, unfortunately it is a hidden feature so you will need to disable this via SharePoint 2013 management shell. The powershell script below should help, run this, it will disable the SharePoint 2013 developer feature and Viola you have a working Content Query web part.

------- Start disable developer feature command -------------

Disable-SPFeature -identity  "E374875E-06B6-11E0-B0FA-57F5DFD72085" -URL http://yoursiteurl

------- Endable developer feature command -------------

Once you have configured your content query web part you can re-enable the developer feature if required using the script below.

------- Start enable developer feature command -------------

enable-SPFeature -identity "E374875E-06B6-11E0-B0FA-57F5DFD72085" -URL http://yoursiteurl

------- End enable developer feature command -------------

Hopefully we will see a fix in the next Cumulative update for this issue, I'm sure there will be more. About time for a Friday night SharePINT