Crashing Upon Entering Worlds

Any time I open Minecraft the launcher works just fine. Beautiful, even. But when I create a private single-layer world or try to join a Multiplayer server, it loads terrain for half a second to two seconds - everything running smoothly as it seems - before it freezes and crashes, leaving me unable to play my favorite game. How do I fix this? Is it an issue with my graphics card or is this an inherent problem with the game patch I'm running?