That happens sometimes, it's an OLD Minecraft glitch that occurred often in version 1.3~ It happened to me a lot before the update. I'm not exactly sure why. I think the crash is because of two things:
1) Too much MC memory used
2) Your computer may be using too much internal memory. Which causes bad lag. A way for everyone to fix lag is simple and MC will crash less.
If anyone wants to know what the lag fix is, just let me know and I will give a tutorial right here~!
Just for clarification, I'll give you guys the main causes of lag:
1) (not everyone) Sometimes, PC or laptop performance can decrease over time and this will drop the frames per second limit slowly. This is easily fixed using my method and there shouldn't be any lag using the method I goofed off with.
2) Low sensitivity
3) Because the worlds are huge and the graphics are incredibly detailed, this requires a lot more CPU memory. Rain and snow have many particles, and because there are many of them running at once. Jungles have so much to load. Ravines because of lava, water, and ores generating just before your eyes.
4) It also depends on how well your computer runs Java. If it doesn't run Java well, this will cause lag and I have yet to see how to fix this. However I will tell all of you, I would download Firefox instead of Internet Explorer. Firefox can run programs much easier and smoother. I would do the occasional cleanup and program updates. Take care of your cpu and it will reward you with smooth running programs and excellent performance.
5) If your computer is unprotected by an antivirus, you may be possessing a malicious coding on your cpu with a 'secret' virus that hides itself among files called malware. I would revitalize/get an antivirus ASAP.
