How would this cause the server to crash for two hours? When the server reboots or changes maps, noblock reverts back to off state.

We have noticed the noblock seems to be turning itself on automatically for certain maps, though. We guessed you had done this for certain escape maps.

On a similar note, I did a fact finding mission earlier tonight, jumping on various servers with a lot of people (32+), ranging from other ZM servers to pubs, and I was just watching the IN field on net_graph 3 and the kbps. I found that the IBIS ZM is sending a lot more packets than other servers, but almost a factor of two or three.

Sending more packets means the server is doing more work. Could be why things are so unstable.