Momentary, multiple bright flashes in the sky.

Momentary bright flashes in the sky.  It occurred four times at uneven intervals over a one hour period, approximately 0130 - 0230 early morning 1/29/2012.  The first three flashes were approximately 5-10 minutes apart; the last occurred about 30 minutes later.  Broken cloud cover and relatively low ceiling sky condition.  Flash effect (shadowing) and intensity (brightness) were similar to what would be expected of a camera flash discharging within about 50 feet of my bedroom window except appeared to originate from the sky, entering my window downward.  No aircraft could be heard - I listened carefully and looked for one.  No vehicle or pedestrian activity on my street at that time - again, I got up, listened, and looked.  No known thunder storm activity in the local vicinity.  No immediate explanation for this.  My oldest son witnessed it once before about a month ago during the holidays.  He was standing outside when it happened.  He claims it was brighte! r than I described.