Please see
http://forum.piwik.org/index.php?showtopic…;st=0#entry3012
Piwik appears to default to using a local socket (pipe) if the DB host is left at the default ‘localhost’ during Install Step #3. Local sockets are often blocked on shared hosting servers; this results in a (highly-cryptic) MySQL error #111. Setting host to ‘127.0.0.1’ appears to force Piwik Install to connect via TCP port instead, which works.
Suggest considering changing ‘localhost’ default on Install form to ‘127.0.0.1’, and/or suggesting the user tries the other alternative if a connection error is returned?