First off, I am using 1.6.57, doesn't seem to be in the official versions list here ?!?...

If I try to start the game, doesn't matter wheter from the installed minecraft or the standalone exe, it fail to start because of a, what I guess, naming conflict of some sort? Anyways, it will download the game fine, but then during launch, it will crash with a java.io.FileNotFoundException for the twitch integration jar, which seems to be in the wrong folder. Trying to manually rename the folder and the file doesn't help, since the launcher will create it's own folder again on launch. Restarting the launcher doesn't help, reinstalling doesn't help, deleting all minecraft related files doesn't help either. Didn't happen before I wanted to do a clean install...

I attached the full launcherlog, there doesn't seem to be a file, so I just copied it out of the launcher and made one myself pretty quick.