Can anyone see what's wrong with this PHP PDO statement

Question

Can anyone see what I'm doing wrong here? I'm getting:

SQLSTATE[42000]: Syntax error or access violation: 1064 You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'INSERT INTO userDevice (userID, deviceID, deviceName, deviceOS, deviceOSVersion,' at line 1

It was working fine when I used seperate parameters for the INSERT & the UPDATE but I swapped to user vars to cut the number of bound parameters..

private function saveDeviceData($userID,$deviceID,$deviceName,$deviceOS,$deviceOSVersion)
    {
    $sql = "SET @did = :did, @dname = :dname, @dos = :dos, @dver = :dver;";
    $sql .= "INSERT INTO userDevice (userID, deviceID, deviceName, deviceOS, deviceOSVersion, timestamp) VALUES(:uid, @did, @dname, @dos, @dver, NOW())";
    $sql .= " ON DUPLICATE KEY UPDATE deviceID = @did, deviceName = @dname, deviceOS = @dos, deviceOSVersion = @dver, timestamp = NOW()";
    try {
        $ps = $this->db->prepareStatement($sql);
        $ps->bindParam(":uid",$userID, PDO::PARAM_INT);
        $ps->bindParam(":did",$deviceID, PDO::PARAM_STR);
        $ps->bindParam(":dname",$deviceName, PDO::PARAM_STR);
        $ps->bindParam(":dos",$deviceOS, PDO::PARAM_STR);
        $ps->bindParam(":dver",$deviceOSVersion, PDO::PARAM_STR);
        $ps->execute();
        return TRUE;
        }
    catch (PDOException $e)
        {
        $this->error("PDO Error: ".$e->getMessage());
        $this->validationError($this->kInvalidEmailOrPasswordMessage);
        return FALSE;
        }
    }