Put the summary of the bug you're having here

What I expected to happen was...:
Minecraft to start up, as usual

What actually happened was...:
An Updating Minecraft window comes up and updates with various texts including "field, downloading update file, Cleaning up..." under "Updating launcher bootstrap..." but then will close and start the whole process again.  

Steps to Reproduce:
1. I open Minecraft
2. The Updating Minecraft window opens
3. The window refreshes with various texts rotating between "field, downloading update file, cleaning up..." and closes and re-opens with same text and goes on a loop until I try to intervene to Force Quit or click onto another window/program to force it to pause long enough to take a screenshot...