HOUSTON -- For the board of directors at NRG Energy Inc., December in recent years meant a trip to the Houstonian. From its gingerbread houses to caroling children, the hotel in this capital city of the Texas energy industry is an attraction during the holidays. There were plenty of reasons to come to town. The Princeton, N.J.-based power producer has a fleet of coal and gas plants in Texas, and a couple of thousand of NRG's employees live and work in the area. But last December, David Crane, who had been the chief executive of NRG since 2003, had reason to be anxious.