Hmm, that was weird. I delete the launcher (AGAIN) and re-downloaded it, I made sure the console was up when I started my world and it actually loaded =D.
I did see in the console that there were some errors such as getting a recipe for mekkanism, also something about "Call getItem failed" for some items, but the world loaded.
By the way, I restarted my computer shortly before opening the world and my computer had to do an update, so I am thinking that somehow helped me? I have to see if the world will continue to work or if this become a problem again.
Also, try making sure you have the latest launcher (431)
Hopefully your world will start to work again for you. Might be one of those technical difficulties where you take break and it fixes itself.
---I noticed that settings such as sort keys/middle click got reset to their default setting, it put me back into cheat mode, and it restarted the acheivement system