Brakes Locking up

Hey i just was driving my jeep and noticed everytime i pressed the brakes they locked up. I checked my mico brake and it was turned off, but everytime i flipped the lever up and down on my mico brake the brakes would release. Any one that can share their knowledge on the issue would be greatly appreciated...
Also just this year i replaced my Master Cylinder.

p.s. i use my jeep as a daily driver to and from school and haven't had this issue till today.