schinbones

Does anyone know if it is ok with the FAA to take a GPS receiver on a commercial airline flight? I an going on a long trip and thought it might be neat to take my Magellan Sportrack. Also, will the altitiude affect the unit adversely in any way? Someone told me that they took theirs once and it malfunctioned and that they had to "re-program" it. Any concerns with that?