Front Brake failure

2007 VRSCX Brembo Brakes
Running along yesterday and approaching a traffic light I proceeded to slow down using my front brake when suddenly the brake lever pulled back all the way to the grip and no braking action whatsoever.
I used the rear brake to stop successfully.
Sitting at the light I pumped the brake lever and it built up pressure and I had front brakes again. Brake has been fine since.
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A little chronology:
A 1500 miles or so ago I installed Speed Bleeders and flushed the brakes completely. The Master cylinder was drained of fluid and I also cleaned the calipers while at it. I had a small issue of getting the air out of the system but I had full pressure on the levers. I ran for about 1500 miles before I suffered this failure. No problems since.
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Inspection of the braking system did not show any leaks in the lines,Master cylinder, bleeders or calipers. Everything was dry as a bone.
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What could cause a problem like this? More importantly what is the cure? I am leaning toward a master cylinder failure of some sort but what?
Any comments would be appreciated.