I just upgraded a site from EE 2.5.5 to 2.8.1 and I get this error after I try to login:
Unable to load the requested class: services_json
I have searched and found reference to Zoo Members and Field Editor, neither of which I have on this site.
I did some additional searching and found a file in Expressionengine/libraries/services_json.php in the 2.5.5 install files that I backed up. However, I can't find anything that would reference this file. If I add the file I can log in but I get a white screen, without the file I get the error message. Either way I am toast.
Insight are most welcome.