I agree with Eric (CITIVOLUS.)
A few years ago, I too saw a similar thing, both from my home near Gosford, and from a dark sky site in NSW. The flash interval was in my case , approx.15 seconds from memory . Appearing "almost" stationary in the sky while the stars kept moving due to earths rotation.
At the time, I called the Sydney observatory and got an answer machine with no reply afterward.
I then called a member of the Astronomical Society of NSW who was at their Observatory near Kurrajong NSW, who saw the flashing at the same interval, but at a different point in time ( due to a diff. observation location ).
From this we decided it was indeed a satellite spinning and reflecting sun-light back from itself.
I then also called the observatory at Buckety ( west of Gosford ) and spoke to a very helpful and interested person who actually plotted the path of this satellite over many hours, and who also phoned me the next day to say it was a satellite called KIKU 6.
A Japanese satellite launched in the early 1990's, that had failed to enter its Geosynchronous orbit as its last engine or stabilising rocket did not fire correctly.
It is now spinning out of control between 8000 Klm's and 18000 Klm's from earth on a very interesting egg shaped orbit.
I have witnessed this many times over the years in the Northern sky.
It would be very possible that there could be more such failed satellites up there also reflecting light toward us on earth.
Hope this helps.
Flashing light in Taurus or Geosynchronous Satellite?
Venessa and 
as Geoff says in his post it is most proberbly what is classed as space junk
I have seen what I call flashers many times in my observing lifetime.
Flashing light anomalies
