Random world loading crashes

After your world loading "enhancement" the loading now is slower than speed from first builds. But in build 7 I can, sometimes, get a "Loading world..." blocked and then the crash. If I open again that world, MAYBE I can enter normally the world but third time works in most of cases. I really hate this. Every world is now more laggy after the "enhancement" and redstone lamps connected to loops make FPS draining , for example from 60 to 19. There is a lighting system problem because, again, you added a "better" lighting system but is NOT better, it's worst! I have 1 GB of RAM and a Quad-Core 1.2 GHz processor.