sky-high. why experts warn that winter vacation could cost you more. and making a difference for a lot of kids by fulfilling the dream one extraordinary young woman never got the chance to see come true. captions paid for by nbc-universal television good evening. the grave security chal edges the u.s. faces overseas are mounting tonight over the anti-islam film and disagreement over what really happened in libya to new saber-rattling between israel and iran. now a series of deadly attacks on u.s. and coalition troops in afghanistan, including two more inside attacks by afghan police. in all, eight troops have died, including six americans. the number of american and nato troops killed this year by afghan security forces has climbed to 51. tonight the chairman of the joint chiefs of staff, general martin dempsey, is calling the so-called blue on green attacks a serious threat to the war effort. our team has it all covered. we begin in kabul with nbc s chief foreign corresp