I recently bought and installed Minecraft, and am not running any mods. For the past few days its been working fine, but last night I tried to load it and the screen wouldn't change beyond the "Loading World, Building Terrain" screen. If I wait a very long time, sometimes it jumps back to the world selection screen, but clicking my world again just takes it to the same place. I've heard that Minecraft uses a lot of RAM and I tried pasting "-Xmx2048M -Xms2048M" into the profile editor to allot more space, but that seems to not have changed anything.
I can't figure out what's wrong, because to my knowledge nothing differed between playing it yesterday afternoon and playing it yesterday evening, but it just won't work now.