I suspect these are all the same thing, It caused a series of rolling crash until the affected player stopped trying to log in.

https://gist.github.com/7492c5467cfadea40a11d581915efe69
https://gist.github.com/a4908a098f74853755e3ae6f463fe9dd
https://gist.github.com/68dd8c6584c3bdca343fcca210414b26
https://gist.github.com/e17fdfb3a4073565e3db2ea23c878789
https://gist.github.com/067ede926fb8611bbdf8847e2c430189
https://gist.github.com/68a491918bbd77869e11ad1c3e987d89
https://gist.github.com/5c97a8c352042e341e6eacaf783d3792
https://gist.github.com/2bfa016edb74d730ec2df0e61a0ea1ae
https://gist.github.com/d8495669691f898674a1b43669bc5a5e
https://gist.github.com/7727dbd6e3bdfa45958231e44be9e299
https://gist.github.com/e7b6428043e3a8ca976784ec4ab83474

You can probably fix it by setting the block at 51766,65,157 to air using mcedit.

Unless they find a way to reproduce this i can't really fix this though, no idea what would cause that.