Unresponsive Server

Hi! I have a server I run off my Mac, and sometimes, while playing on it, it completely blanks out, and is unreachable. I can't stop it via console because it doesn't accept commands, so the only way to turn it off and restart it is to close the terminal window, and force quit everything, but then all the world data gets lost. If anyone could help, that would be awesome. Thanks in advanced!

Also, when I go to Activity Monitor, it says the Java proccess is taking up anywhere from 150-380% of my CPU, so... yeah.
--UPDATE--
I finally got a response from my server, but it says: http://pastie.org/7913932 I get that error a couple times a month.. where it says exception in thread #
--UPDATE 2--
Now it says: http://pastie.org/7913937 what does that mean???

EDIT by Moderator: merged posts, please use the edit button instead of double posting.