Multiverse is Broken

I had Multiverse and Multiverse-Portals set up on my server. I encountered no problems with it until one day I started up the server and it shut itself down and crashed. I realized that Multiverse was out of date, so I downgraded my server from 1.4.7 to 1.4.5. Or at least, that's what I thought. Whatever I did fixed the problem, for a little while, but the server didn't actually downgrade, and it crashed again. Someone gave me a link (http://ci.onarandombox.com/job/Multiverse-Core/) to a place were I could get an up to date version. Even with that version I have problems. The server is fine when it starts, but after I load up a new world and restart the server, CRASH!

Can someone please help me. I am really desperate!