After being in the nether for a while (~2 hours or so), the game will start regularly crashing whenever I am in the Nether. The crashes can happen anywhere between 30 seconds after logging in to an hour after logging in. The crashes only occur in the nether- the game runs fine in the overworld.
This has happened on 2 different worlds. The problem occurs both with no extra java arguments and with arguments increasing the max memory to 1GB or 2GB. It happens both with the lwjgl libraries included with Minecraft and the fixed up-to-date libraries.
The crash results in any one of these 3 errors:
Bus Error
Trace/Breakpoint Trap
SIGSEGV (Segmentation Fault)
None of these errors generates a crash report in the .minecraft folder, but the 3rd error (the segmentation fault) generates a log. I have attached one of these logs:
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I installed Java 7, and I'm still getting crashes in the Nether. This time the error message was simply:
Aborted (core dumped)
Actually, ignore my last comment. I was in the java 7 directory, but I ran java (which is still linked to java6) rather than ./java for the java7 in the current directory. I don't have much time right now, but I'll continue running around the nether for a bit and see if I get any more crashes.
Well, I ran a few loops around some nether fortresses for 35 minutes and didn't encounter a crash, so this may have fixed the issue. It's also possible that I simply got lucky as it sometimes can go a while without crashing, but chances are good that using Java 7 fixed the problem.
If that's the case, the Minecraft launcher should do a version check. System.getProperty("java.version") will give you the current java version.

Duplicate of MC-2749 , please use the search function to see if your bug has already been submitted. Currently over 30% of tickets are being closed as duplicate.
This is not a duplicate as my problem is not that a crash occurs immediately upon entering the nether, but that crashes occur regularly while within the Nether.
This appears to be solved now, so you can mark it resolved if you wish. If I encounter this problem again, I will reopen the bug.
Update your java as your version is very outdated.