Minecraft Forums

Backups, keep them. Always.
If you're using Linux to host the server, you can use cronjobs to automatically back stuff up.
This won't help you now, but it could help you in the future (unless you've got some already).

For now, completely shut off the server. Leave it off for about 12 hours (minimum). It will stop the people from attacking it.

Check for updates for all of your plugins and bukkit. If there is a bug, it hopefully has been fixed by now.

Hey, if your host hasn't gotten back to you in a week, it's probably time to switch hosts. Also, I have an idea on what might be your problem. Try to find a "Server JAR" option on your main multicraft screen. (It's on the same page as the ip and port stuff) Make sure it is set to "Mod: Craftbukkit."
Hope this helps!