hi,
it seems there is a problem recording conversions with campaigns.
the referer is empty in the table piwik_log_conversion (referer_type=1 and referer_name=""). conversion statistics for campaigns are wrong.

I replaced those values in the database with referer_type=6 and the correct refer_name and stats are now correct.

here is a sample tracking code I used :

$t = new PiwikTracker( $idSite = 1, 'http://192.168.0.212/piwik12/');
$t->disableCookieSupport();
$t->setip("192.168.1.39");
$t->setUrl('http://example.org/yoyoyo/yo?piwik_campaign=popopoXXXxxx4');
$t->doTrackGoal(1, 3);