I talked to the only player that was on at the time. He said he wasn't doing anything with any chunk loading blocks and he was in the overworld not a mystcraft age/nether/twilight forest/end. I don't have any experience reading these reports but I thought it would be something like that looking at the first section. I tried deleting the mystcraft dim-### folders but it didn't help. I was able to get the server to load a really old backup of the world but we'd all prefer salvaging this copy if anyone has any ideas to try.
http://pastebin.com/embed_iframe.php?i=QZVVdNK3
http://pastebin.com/embed_iframe.php?i=QZVVdNK3