what version of Piwik are you using? I remember a bug like this in an older version. Update to 1.2.1 if not done already. Otherwise, try to login as the “Super User” (the username can be found in your config/config.ini.php if you forgot it)
I’ve updated to 1.2.1 as prompted sometime last week.
I did what you instructed - logging in with the information in my config file but I got an error message stating that my username and password don’t match. Is it advisable to re-install?
Thanks!
EDIT
I clearly have 1.2.1.
So while looking through my server, it is still listed as 1.1.1. o.O