EarthLink’s stake in Helio helped push the company to a loss in the fourth quarter of 2006 and dented its yearly earnings, but executives say the wireless joint venture shows promise. The Internet service provider on Tuesday reported a net loss of $24.8 million, compared with a profit of $29.2 million during the same period a year earlier. The latest quarter included an equity loss of $35.7 million from Helio, EarthLink’s wireless joint venture with South Korea’s SK Telecom, which launched in May. EarthLink said it lost $85 million on the venture for the year.