Sign-in window crashes

So... Just installed Minecraft for Windows 10. The one feature that isn't working for me, Sign In. What happens is I click Sign In; it says it's connecting and everything, then I see a black window pop up for one or two tenths of a second before crashing.

Yes, I tried "turning it off and turning it on again",
It's on Version 1.1.4, not sure if it affects other versions...
Sign-in works fine for my friend,
Yes, I have a good computer,
and Yes, I have an XBOX Live account, which DOES work on my iPad.