Sé que esto se me ha pedido 1000 veces, pero por alguna razón continúo golpeando mi cabeza contra la pared ...

Esto funciona:

$sql = 'SELECT a.eventCode, a.eventTime, a.teamCode, a.playerCode, b.lastName, b.firstName, b.number, a.xCoord, a.yCoord, a.id ';
$sql = $sql . 'FROM events a, players b ';
$sql = $sql . 'WHERE a.regGUID in ( ' . $regGUID . ' ) and ';
$sql = $sql . 'a.playerCode=b.playerCode and a.gameCode = "' . $game . '" order by a.eventTime desc, a.actionCode asc'; 
$stmt = $db->prepare($sql);
$results = $stmt->execute();

Esto no hace:

$sql = 'SELECT a.eventCode, a.eventTime, a.teamCode, a.playerCode, b.lastName, b.firstName, b.number, a.xCoord, a.yCoord, a.id ';
$sql = $sql . 'FROM events a, players b ';
$sql = $sql . 'WHERE a.regGUID in ( :regGUID ) and ';
$sql = $sql . 'a.playerCode=b.playerCode and a.gameCode = :game order by a.eventTime desc, a.actionCode asc'; 
$stmt = $db->prepare($sql);
$stmt->bindValue(':regGUID', $regGUID, PDO::PARAM_STR);
$stmt->bindValue(':game', $game, PDO::PARAM_STR);
$results = $stmt->execute();

¿Qué me estoy perdiendo? Gracias