I found other threads noting similar problems but, not specifically the same. This only appears on certain pages of the site, and on those pages the editing features are disabled.

I don't have Tweetcreet, and I checked config/site.php and it is pointing to the correct updates sub directory.

Do I need to do a manual replace of the core? The site is only 3 years old.

Here are the errors:
Warning: require_once(/home/katevrij/public_html/updates/concrete5.6.1.2_updater/concrete/libraries/datetime_compat.php) [function.require-once]: failed to open stream: No such file or directory in /home/katevrij/public_html/updates/concrete5.6.1.2_updater/concrete/core/libraries/loader.php on line 30

Fatal error: require_once() [function.require]: Failed opening required '/home/katevrij/public_html/updates/concrete5.6.1.2_updater/concrete/libraries/datetime_compat.php' (include_path='/home/katevrij/public_html/libraries/3rdparty:/home/katevrij/public_html/updates/concrete5.6.1.2_updater/concrete/libraries/3rdparty:.:/usr/local/lib/php') in /home/katevrij/public_html/updates/concrete5.6.1.2_updater/concrete/core/libraries/loader.php on line 30

This is the site:http://katevrijmoet.com