I had to take my site down due to a malware infection--god timing in a way since I am about to update it with a new template, etc.
So I did a clean install with Rocketlauncher. Looks good.
Then I change the config file to point to my old database--isn't that how you do it? when I do this I get a sort of generic looking front end and, after I try to log in, this error on the back:
Fatal error: Call to undefined method stdClass::onAuthenticate() in....
If I change config back the demo is still there. Same sql host.
Fatal error: Call to undefined method stdClass::onAuthenticate() in .../libraries/joomla/user/authentication.php on line 121
It also happens when I try to log in to the "site down" login form when I have the "corrected" database in the config file but use the incorrect user name...
I am not sure this is the template issue as I can't replicate the same problem. I found a thread in Joomla forum
forum.joomla.org/viewtopic.php?f=431&t=276235
The problem might be related to the database or improper/incomplete uploaded files