Sounds like a corrupted chunk. But since sk doesn't look here for fixing bugs, I suggest you post here http://skcraft.com/forums/crash-issues/ (and possibly delete this thread if you just copy and paste it over to the other section. Since we don't want copies of threads on the forums)
The crash log however shows Java randomly exiting with an error code of 133. I'm not at my computer so I can't check if the error is caused by something specific. A google search showed some results, although about a different Java application, about a missing import so the OP might now be using a proper launcher. I suggested force updating because there was a message about a missing file in the log.
Running latest client and launcher, I doubt it is related since I was playing fine until walked into that area. Should I delete this thread?? Wouldn't it be better to move it to the other subforum? EDIT:Just launched it again, the log is pretty much the same except that the exit code is 139 now. Edit2: Force updated, same thing all over.