It appears that no matter what I do, I cannot play Minecraft, in any form. This started when I first noticed after attempting to play the FTB Modpack for Horizons, which produced errors on attempting to login to servers and worldgen, along with crashes relating to a "Bouncy Castle" provider that was invoked by minecraft.net.

I also attempted to get on SSP Vanilla, 1.7.4, with similar results. Worldgen Crashes, cannot login to servers, nor can I play on SSP worlds.