After upgrading concrete to 5.6.1.2, I'm unable to add a block to a newly created page. I can edit existing blocks on existing pages but attempting to create a new block yields the following error:

Warning: require_once(/home2/nhclifeo/public_html/updates/concrete5.6.1.2_updater/concrete/models/json.php) [function.require-once]: failed to open stream: No such file or directory in /home2/nhclifeo/public_html/updates/concrete5.6.1.2_updater/concrete/core/libraries/loader.php on line 48

Fatal error: require_once() [function.require]: Failed opening required '/home2/nhclifeo/public_html/updates/concrete5.6.1.2_updater/concrete/models/json.php' (include_path='/home2/nhclifeo/public_html/libraries/3rdparty:/home2/nhclifeo/public_html/updates/concrete5.6.1.2_updater/concrete/libraries/3rdparty:.:/usr/lib64/php:/usr/lib/php') in /home2/nhclifeo/public_html/updates/concrete5.6.1.2_updater/concrete/core/libraries/loader.php on line 48