Rear Tires Suddenly Lock Up Going 65

I like the brakes posts, especially the master cyl adjuster post.
Think about it.
The seal in the master cylinder could be past the point in it's bore to not let the fluid come back from the wheel cylinders.
It would just move the fluid back and forth to the brakes but not let new fluid in or out of the lines.
At a good road speed the lines got heated by the engine and exhaust causing a hydraulic lock.
If this happened it was probably all four wheels but the backs lock up sooner and there ya go.

Hmmm