I'm having this problem as well. I've redownloaded the launcher, Deleted the launcher and the .techniclauncher folder.
The launcher STILL only goes to "Downloading launcher 0/3" and INSTANTLY closes.
Edit : There's a solution in the sticky. Going to try that. Nope, doesn't work. Says that it's corrupt. (It's done this every time I've tried to open it, I've reinstalled it about 3 times.)