Hello,
I updated to concrete 5.6.2.1 and the main page is working good, but the other pages that use another theme are returning the text below.
I desperately come to ask you help to find what gives me this fatal error:

"Warning: : failed to open stream: No such file or directory in blablabla\concrete5.6.2.1_updater\concrete\core\libraries\loader.php on line 297
Fatal error: require_once(): in blablabla\concrete5.6.2.1_updater\concrete\core\libraries\loader.php on line 297"

I cannot find any other discussion about the same error that can give me a glue to the problem I have now!
That's why I ask 2cents from those who may know the steps to figure it out.

Thank you in advance for,
Shift