Yeah clearing the cache and stuff didn't help me either, now it just throws up a 'HTTPS' error and the launcher completely closes.

And Chiral, I believe you've confirmed another suspicion I have, that this is an issue with XP (I'm also a XP holdout), and.. unfortunately SE dropped support for the game under XP long ago (as did Microsoft), so I've been kind of expecting this sort of thing to happen eventually (game-breaking bug that was XP specific and thus wouldn't be fixed). Of course it might not be operating-system specific, but it's highly likely XP might be at least partially responsible (in that, updating Internet Explorer to the last supported version would fix it, which is not compatible with XP). Ah well...

Looks like it's finally time to put XP to sleep.