Hi there,
I’ve just updated our server from 2.0.3 to 2.2.2, however, I now can’t log in as the Superuser as I get the following frontend error message:
Error: Wrong Username and password combination.
Username and Password are stored in Lastpass so I know that they are correct and haven’t changed.
I’m just wondering if there’s an easy way to recover access (there are no other admin accounts on this installation.)
Hmmm, on checking the DB piwik_user table, I don’t see the superuser account. 
Okay, by changing the superuser access in the DB I was able to recreate the account via the API and undo the superuser access changes.
In Firefox with a whole bunch of privacy plugins and not allowing 3rd party cookies I get the following error message on login:
Error: Form security failed. Please reload the form and check that your cookies are enabled. If you use a proxy server, you must configure Piwik to accept the proxy header that forwards the Host header. Also, check that your Referrer header is sent correctly.
Using IE I don’t have this issue so I’m going to have to go through disabling stuff to find where the issue lies.