RuneK

Movie with Iridium flares: http://www.universetoday.com/116598/flash-iridium-flares-captured-in-real-time-by-thierry-legault/

There are a lot of debris in orbit that can reflect light. I see something like that quite often, and it has increased over the years as space debris and sattelites has increased in numbers. Some flashes can be very bright, and some seems to tumble along, leaving periodic flashes. More on wiki: http://en.wikipedia.org/wiki/Space_debris